refactor(service,scanner): return concrete types from constructors

Apply the Go best-practice convention 'accept interfaces, return concrete
types' across the service and scanner packages:

- NewBrowseService           -> *browseService
- NewWriteService            -> *writeService
- NewMediaStreamer           -> *mediaStreamer
- NewFSScanner               -> *FSScanner
- NewFSScannerWithLogger     -> *FSScanner
- NewPodcastBrowseService    -> *podcastBrowseService
- NewTagService              -> *tagService
- NewShareService            -> *shareService
- NewProgressService         -> *progressService
- NewAdminService            -> *adminService
- NewAdminServiceWithLogger  -> *adminService
- NewAuthService             -> *authService
- NewNoteService             -> *noteService
- NewFavService              -> *favService
- NewMediaService            -> *mediaService
- NewMediaServiceWithPodcastBrowser -> *mediaService

Callers continue to work unchanged because Go allows assigning a concrete
type to an interface variable. All tests pass with -race -cover.

12 files changed, 16 insertions, 16 deletions

diff --git a/internal/scanner/scanner.go b/internal/scanner/scanner.go
index d1e50ba..15a4949 100644
--- a/internal/scanner/scanner.go
+++ b/internal/scanner/scanner.go
@@ -38,12 +38,12 @@ type FSScanner struct {
 }
 
 // NewFSScanner creates a filesystem scanner with injected dependencies.
-func NewFSScanner(store repository.ScannerStore, prober probe.Prober, thumbGen thumb.Generator, clk clock.Clock, mediaRoot string) Scanner {
+func NewFSScanner(store repository.ScannerStore, prober probe.Prober, thumbGen thumb.Generator, clk clock.Clock, mediaRoot string) *FSScanner {
 	return NewFSScannerWithLogger(store, prober, thumbGen, clk, mediaRoot, slog.Default())
 }
 
 // NewFSScannerWithLogger creates a filesystem scanner with an injected logger.
-func NewFSScannerWithLogger(store repository.ScannerStore, prober probe.Prober, thumbGen thumb.Generator, clk clock.Clock, mediaRoot string, logger *slog.Logger) Scanner {
+func NewFSScannerWithLogger(store repository.ScannerStore, prober probe.Prober, thumbGen thumb.Generator, clk clock.Clock, mediaRoot string, logger *slog.Logger) *FSScanner {
 	if logger == nil {
 		logger = slog.Default()
 	}
diff --git a/internal/service/admin.go b/internal/service/admin.go
index 11406b8..1b1a352 100644
--- a/internal/service/admin.go
+++ b/internal/service/admin.go
@@ -21,12 +21,12 @@ type adminService struct {
 }
 
 // NewAdminService creates a concrete AdminService.
-func NewAdminService(store repository.AdminServiceStore, clk clock.Clock, hasher auth.Hasher, sc scanner.Scanner, mediaRoot string, appCtx context.Context) AdminService {
+func NewAdminService(store repository.AdminServiceStore, clk clock.Clock, hasher auth.Hasher, sc scanner.Scanner, mediaRoot string, appCtx context.Context) *adminService {
 	return NewAdminServiceWithLogger(store, clk, hasher, sc, mediaRoot, appCtx, slog.Default())
 }
 
 // NewAdminServiceWithLogger creates a concrete AdminService with an injected logger.
-func NewAdminServiceWithLogger(store repository.AdminServiceStore, clk clock.Clock, hasher auth.Hasher, sc scanner.Scanner, mediaRoot string, appCtx context.Context, logger *slog.Logger) AdminService {
+func NewAdminServiceWithLogger(store repository.AdminServiceStore, clk clock.Clock, hasher auth.Hasher, sc scanner.Scanner, mediaRoot string, appCtx context.Context, logger *slog.Logger) *adminService {
 	return &adminService{
 		trashService:           NewTrashService(store),
 		scanService:            NewScanService(appCtx, sc, mediaRoot, clk, logger),
diff --git a/internal/service/auth.go b/internal/service/auth.go
index b5f2720..56210b2 100644
--- a/internal/service/auth.go
+++ b/internal/service/auth.go
@@ -19,7 +19,7 @@ type authService struct {
 }
 
 // NewAuthService creates a concrete AuthService.
-func NewAuthService(store repository.AuthServiceStore, clk clock.Clock, hasher auth.Hasher, sm auth.SessionManager) AuthService {
+func NewAuthService(store repository.AuthServiceStore, clk clock.Clock, hasher auth.Hasher, sm auth.SessionManager) *authService {
 	return &authService{
 		store:  store,
 		clock:  clk,
diff --git a/internal/service/browse.go b/internal/service/browse.go
index 4f70717..6308e1a 100644
--- a/internal/service/browse.go
+++ b/internal/service/browse.go
@@ -36,7 +36,7 @@ type podcastBrowseService struct {
 }
 
 // NewPodcastBrowseService creates a PodcastBrowser backed by a PodcastRepo.
-func NewPodcastBrowseService(store repository.PodcastRepo, mediaRoot string) PodcastBrowser {
+func NewPodcastBrowseService(store repository.PodcastRepo, mediaRoot string) *podcastBrowseService {
 	return &podcastBrowseService{store: store, mediaRoot: mediaRoot}
 }
 
@@ -77,7 +77,7 @@ func (p *podcastBrowseService) AugmentBrowseSet(ctx context.Context, result *Bro
 }
 
 // NewBrowseService creates a BrowseService.
-func NewBrowseService(store repository.BrowseServiceStore, clk clock.Clock, mediaRoot string, helper *accessHelper, browser PodcastBrowser) MediaBrowseService {
+func NewBrowseService(store repository.BrowseServiceStore, clk clock.Clock, mediaRoot string, helper *accessHelper, browser PodcastBrowser) *browseService {
 	return &browseService{
 		store:          store,
 		clock:          clk,
diff --git a/internal/service/fav.go b/internal/service/fav.go
index 57dcb73..e8b8ab9 100644
--- a/internal/service/fav.go
+++ b/internal/service/fav.go
@@ -13,7 +13,7 @@ type favService struct {
 }
 
 // NewFavService creates a FavService.
-func NewFavService(store repository.FavoriteServiceStore, helper *accessHelper) MediaFavoriteService {
+func NewFavService(store repository.FavoriteServiceStore, helper *accessHelper) *favService {
 	return &favService{
 		store:  store,
 		helper: helper,
diff --git a/internal/service/media.go b/internal/service/media.go
index 4fea78c..38c670f 100644
--- a/internal/service/media.go
+++ b/internal/service/media.go
@@ -29,12 +29,12 @@ type mediaService struct {
 }
 
 // NewMediaService creates a concrete MediaService by wiring role-focused sub-services.
-func NewMediaService(store repository.MediaServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober) MediaService {
+func NewMediaService(store repository.MediaServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober) *mediaService {
 	return NewMediaServiceWithPodcastBrowser(store, clk, mediaRoot, thumbGen, prober, nil)
 }
 
 // NewMediaServiceWithPodcastBrowser creates a MediaService with an optional PodcastBrowser.
-func NewMediaServiceWithPodcastBrowser(store repository.MediaServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober, browser PodcastBrowser) MediaService {
+func NewMediaServiceWithPodcastBrowser(store repository.MediaServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober, browser PodcastBrowser) *mediaService {
 	helper := &accessHelper{store: store}
 	return &mediaService{
 		MediaBrowseService:   NewBrowseService(store, clk, mediaRoot, helper, browser),
diff --git a/internal/service/note.go b/internal/service/note.go
index da7f923..56409d6 100644
--- a/internal/service/note.go
+++ b/internal/service/note.go
@@ -16,7 +16,7 @@ type noteService struct {
 }
 
 // NewNoteService creates a NoteService.
-func NewNoteService(store repository.NoteServiceStore, clk clock.Clock, helper *accessHelper) MediaNoteService {
+func NewNoteService(store repository.NoteServiceStore, clk clock.Clock, helper *accessHelper) *noteService {
 	return &noteService{
 		store:  store,
 		clock:  clk,
diff --git a/internal/service/progress.go b/internal/service/progress.go
index 376ebb7..ef248cf 100644
--- a/internal/service/progress.go
+++ b/internal/service/progress.go
@@ -17,7 +17,7 @@ type progressService struct {
 }
 
 // NewProgressService creates a concrete ProgressService.
-func NewProgressService(store repository.ProgressServiceStore, clk clock.Clock) ProgressService {
+func NewProgressService(store repository.ProgressServiceStore, clk clock.Clock) *progressService {
 	return &progressService{
 		store: store,
 		clock: clk,
diff --git a/internal/service/share.go b/internal/service/share.go
index 9032f8c..9552031 100644
--- a/internal/service/share.go
+++ b/internal/service/share.go
@@ -22,7 +22,7 @@ type shareService struct {
 }
 
 // NewShareService creates a ShareService.
-func NewShareService(store repository.ShareServiceStore, clk clock.Clock, helper *accessHelper) MediaShareService {
+func NewShareService(store repository.ShareServiceStore, clk clock.Clock, helper *accessHelper) *shareService {
 	return &shareService{
 		store:  store,
 		clock:  clk,
diff --git a/internal/service/streamer.go b/internal/service/streamer.go
index e04293e..a0c09b0 100644
--- a/internal/service/streamer.go
+++ b/internal/service/streamer.go
@@ -16,7 +16,7 @@ type mediaStreamer struct {
 }
 
 // NewMediaStreamer creates the default service for preparing media files for HTTP streaming.
-func NewMediaStreamer(remuxer probe.Remuxer) MediaStreamer {
+func NewMediaStreamer(remuxer probe.Remuxer) *mediaStreamer {
 	return &mediaStreamer{remuxer: remuxer}
 }
 
diff --git a/internal/service/tag.go b/internal/service/tag.go
index d08c387..88e19b6 100644
--- a/internal/service/tag.go
+++ b/internal/service/tag.go
@@ -16,7 +16,7 @@ type tagService struct {
 }
 
 // NewTagService creates a TagService.
-func NewTagService(store repository.TagServiceStore, helper *accessHelper) MediaTagService {
+func NewTagService(store repository.TagServiceStore, helper *accessHelper) *tagService {
 	return &tagService{
 		store:  store,
 		helper: helper,
diff --git a/internal/service/write.go b/internal/service/write.go
index 8508951..f2f5080 100644
--- a/internal/service/write.go
+++ b/internal/service/write.go
@@ -29,7 +29,7 @@ type writeService struct {
 }
 
 // NewWriteService creates a WriteService.
-func NewWriteService(store repository.WriteServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober, helper *accessHelper) MediaWriteService {
+func NewWriteService(store repository.WriteServiceStore, clk clock.Clock, mediaRoot string, thumbGen thumb.Generator, prober probe.Prober, helper *accessHelper) *writeService {
 	return &writeService{
 		store:     store,
 		clock:     clk,