docs: api comments say what the endpoints do, not how they came to be (#6277)

Rewrites the internal/api comment blocks to rule 32: task, milestone and
rule ids gone, the stories behind them restated as the constraint they
left, stale references corrected (the stream secret is wired from config,
the timezone handler already refreshes the scheduler, the Android app is
the native client, the design docs cited are not in the repo). Also
rewraps comment lines over 80 columns left by the earlier batches.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/admin_covers.go

@@ -19,8 +19,9 @@ type adminCoverRefetchResp struct {
 	CoverArtSource *string `json:"cover_art_source"`
 }
 
-// handleAdminAlbumRefetchCover implements POST /api/admin/albums/{id}/cover/refetch.
-// Synchronously clears + re-runs the enricher for one album.
+// handleAdminAlbumRefetchCover implements POST
+// /api/admin/albums/{id}/cover/refetch. Synchronously clears + re-runs the
+// enricher for one album.
 func (h *handlers) handleAdminAlbumRefetchCover(w http.ResponseWriter, r *http.Request) {
 	albumID, ok := parseUUID(chi.URLParam(r, "id"))
 	if !ok {
@@ -51,9 +52,9 @@ type adminBulkRefetchResp struct {
 	Started bool `json:"started"`
 }
 
-// handleAdminBulkRefetchCovers implements POST /api/admin/covers/refetch-missing.
-// Returns immediately; the drain runs UNBOUNDED in a background goroutine
-// (#388 — no global cap; remote providers self-throttle per provider, local
+// handleAdminBulkRefetchCovers implements POST
+// /api/admin/covers/refetch-missing. Returns immediately; the drain runs
+// UNBOUNDED in a background goroutine (remote providers pace themselves, local
 // sources run at disk speed). The count is unknowable synchronously, so the
 // response just acknowledges the drain started.
 func (h *handlers) handleAdminBulkRefetchCovers(w http.ResponseWriter, _ *http.Request) {