Add circuit breaker / backoff for failing podcast feeds in CheckFeeds

- DB: add consecutive_failures and next_check_at to podcast_feeds
- model: add ConsecutiveFailures and NextCheckAt to PodcastFeed struct
- repository: update CRUD queries to handle new columns and
  ListFeedsNeedingCheck to skip feeds with future next_check_at
- service: update CheckFeeds to use new query, update checkFeed to
  reset counters on success and increment exponential backoff on failure
- tests: adapt mock signatures, add backoff integration test

1 files changed, 2 insertions, 0 deletions

diff --git a/internal/model/podcast.go b/internal/model/podcast.go
index 8b5c3a2..f0b016d 100644
--- a/internal/model/podcast.go
+++ b/internal/model/podcast.go
@@ -15,6 +15,8 @@ type PodcastFeed struct {
 	LastETag             string     `json:"last_etag"`
 	CheckIntervalMinutes int        `json:"check_interval_minutes"`
 	AutoDownload         bool       `json:"auto_download"`
+	ConsecutiveFailures  int        `json:"consecutive_failures"`
+	NextCheckAt          *time.Time `json:"next_check_at"`
 	CreatedAt            time.Time  `json:"created_at"`
 }