feat(admin): all-podcasts view — disk-first maintenance for every feed

§0 item 8 (Phase-4 item 1 pulled forward, user directive: maintenance
tooling ships WITH the features it maintains):

- /admin/podcasts (AdminMiddleware): every feed from EVERY user via the
  RLS admin escape (first-admin identity, poller/fetcher contract) —
  feed + host, library, subscriber count/names, downloaded/total, DISK
  USAGE, last fetch. Sorted disk DESC ('what's eating the disk'),
  totals header (feeds · episodes · bytes on disk).
- Per-feed actions: Refresh · Delete files (rows → pending, disk freed;
  confirms spell out the re-materialization contract) · Remove feed
  (rows + files for everyone — the same admin delete as the detail
  page). All confirms ride the global confirm modal.
- New sqlc: ListAllPodcastFeedsAdmin (correlated aggregates),
  ResetPodcastEpisodeFileDeleted / ResetPodcastFeedFilesDeleted —
  downloaded rows reset to pending with download-derived facts cleared
  (audio_metadata, chapter_count, cover, size, mime); file_path KEPT
  (fetch-maintained layout — a re-download lands on the same path).
  file deletion via the existing DeleteFeedFiles file-removal pattern
  (episode files + .cover.jpg siblings).
- Poll upsert never touches download_state, so deleted files STAY
  deleted — a feed refresh re-lists metadata but re-materializes
  nothing (pinned by TestAdminDeleteEpisodeFiles).
- Per-episode admin delete-file: POST /feeds/:id/episodes/:eid/
  delete-file (admin) — one episode's file gone, row pending, siblings
  untouched; HX swaps the episode list. (Found while testing: the
  handler first read c.Param("id") — the FEED's uuid — instead of
  :eid; the 404 'episode not found' trail led straight to it.)
- Tests: admin sees other users' feeds + subscriber names; regular
  users 403 on page AND actions; single + feed-level deletion reset
  rows/clear facts/delete files; refresh leaves pending rows pending.
- Admin nav gains 'Podcasts' under Administration.

Wrong-gotcha note for future agents: parseUUID on c.Param('id') inside
a /feeds/:id/episodes/:eid route resolves the FEED, not the episode.

internal/database/queries/queries.sql

@@ -4698,6 +4698,68 @@ WHERE feed_id = $1;
 -- name: CountPodcastFeedSubscribers :one
 SELECT COUNT(*) FROM podcast_subscriptions WHERE feed_id = $1;
 
+-- name: ListAllPodcastFeedsAdmin :many
+-- Admin all-podcasts view (§0 item 8 / Phase-4 item 1): EVERY feed from
+-- EVERY user with its maintenance aggregates. Runs under the first-
+-- admin identity (invariant 12 — same contract as the poller). Sorted
+-- by disk usage DESC: the maintenance question is "what's eating the
+-- disk", so the hogs surface first.
+SELECT f.id, f.title, f.host, f.last_fetched_at, f.library_id,
+       l.name AS library_name,
+       (SELECT COUNT(*) FROM media_items m
+         WHERE m.source_feed_id = f.id AND m.source = 'podcast_episode') AS episode_total,
+       (SELECT COUNT(*) FROM media_items m
+         WHERE m.source_feed_id = f.id AND m.source = 'podcast_episode'
+           AND m.download_state = 'downloaded') AS episode_downloaded,
+       (SELECT COALESCE(SUM(m.file_size), 0)::BIGINT FROM media_items m
+         WHERE m.source_feed_id = f.id AND m.source = 'podcast_episode'
+           AND m.download_state = 'downloaded') AS disk_bytes,
+       (SELECT COUNT(*) FROM podcast_subscriptions s
+         WHERE s.feed_id = f.id) AS subscriber_count,
+       (SELECT COALESCE(string_agg(u.username, ', ' ORDER BY u.username), '')::TEXT
+          FROM podcast_subscriptions s
+          JOIN users u ON u.id = s.user_id
+         WHERE s.feed_id = f.id) AS subscriber_names
+FROM podcast_feeds f
+JOIN libraries l ON l.id = f.library_id
+ORDER BY 9 DESC, f.title ASC;
+
+-- name: ResetPodcastEpisodeFileDeleted :exec
+-- Admin file deletion (§0 item 8): ONE downloaded episode's disk file
+-- was removed — reset the row to pending and clear the download-derived
+-- facts. file_path is deliberately KEPT: it is the fetch-maintained
+-- layout (written at fetch time, not download time), so a re-download
+-- lands on the same path. The poll upsert never touches download_state,
+-- so a deleted file stays deleted (invariant 2: polling never deletes;
+-- admins delete knowingly).
+UPDATE media_items
+SET download_state = 'pending',
+    download_error = NULL,
+    download_attempts = 0,
+    file_size = NULL,
+    mime_type = NULL,
+    cover_image_path = NULL,
+    audio_metadata = NULL,
+    chapter_count = NULL,
+    updated_at = NOW()
+WHERE id = $1 AND source = 'podcast_episode' AND download_state = 'downloaded';
+
+-- name: ResetPodcastFeedFilesDeleted :execrows
+-- Same reset for EVERY downloaded episode of a feed (per-feed
+-- "Delete files" action on the admin view).
+UPDATE media_items
+SET download_state = 'pending',
+    download_error = NULL,
+    download_attempts = 0,
+    file_size = NULL,
+    mime_type = NULL,
+    cover_image_path = NULL,
+    audio_metadata = NULL,
+    chapter_count = NULL,
+    updated_at = NOW()
+WHERE source_feed_id = $1 AND source = 'podcast_episode'
+  AND download_state = 'downloaded';
+
 -- name: ListPodcastFeedsForPolling :many
 -- Poller worklist (admin identity): every feed with its validators and
 -- the back-off flag (is_complete feeds poll rarely, never disappear).