docs(admin): all-podcasts page — the maintenance view

Seventh admin page. Documents the disk-usage sort (hogs surface first),
the header totals, each column's meaning (orphaned = no subscribers,
usually a departed user's feed), and the three actions with their real
semantics: Refresh (manual poll vs. the Settings→Podcasts interval),
Delete files (resets episodes to pending, re-download on demand, and
the non-obvious part quoted: a refresh will not re-materialize them),
Remove (instance-wide: rows + files + everyone's subscriptions, unlike
a user's own unsubscribe). Cross-links the user podcast guide for the
listening side. Glossary gains Delete files and a scoped Remove.

docs/developer/ui-controls.md

@@ -292,6 +292,14 @@ label: Keep this copy
 where: Admin → Hash Conflicts → a copy row
 does: Keeps that copy, folds the other copies' reading data into it, and removes their catalog rows. Files on disk are never touched.
 
+label: Delete files
+where: Admin → All Podcasts → a feed row
+does: Frees the disk and resets downloaded episodes to pending; they re-download on demand. A feed refresh will NOT re-materialize them.
+
+label: Remove
+where: Admin → All Podcasts → a feed row
+does: Admin-wide feed removal — episode rows, downloaded files, and every user's subscription are deleted. Instance-wide, unlike a user's own unsubscribe.
+
 label: Resume rewind
 where: audio player → player settings; profile settings
 does: Rewinds playback a configured few seconds when you resume.