Add reversible administrator room archiving

Organize closed rooms with archive filters, live-authorized atomic receipts and exact saved retries. Preserve saved games, timestamps, credentials, discussion and AI deadlines. Unarchive leaves play closed; reopen requires unarchive, and removal/restoration preserves both flags.

Verified types, lint, 5379 offline tests, 52 HTTP tests and build. Twenty dedicated administrator HTTP groups and independent privacy/persistence review passed. Desktop/mobile browser QA confirmed a single archive after a lost response and refresh, readable recovery text, mobile unarchive and separate reopening, and saved-seat restoration. All 2,049 baseline rooms, 4,348 seats and related records preserved. Authenticated production admin acceptance awaits authorized QA access; full admin and rules gates remain open.

docs/ADMIN_ROOM_REMOVAL.md

@@ -64,7 +64,11 @@ These checks also exposed a lobby readiness bug: a joining human or human
 faction change could clear AI readiness and block start. Those changes now clear
 only human readiness; focused JSON continuation tests and the HTTP start cover it.
 
-Close/end, archive, permanent deletion, bulk operations, participant support and
+[Close/reopen](ADMIN_ROOM_CLOSURE.md) and [archive/unarchive](ADMIN_ROOM_ARCHIVE.md)
+are separate reversible controls. Permanent deletion, bulk operations, participant support and
 backup/import workflows remain unfinished. Recoverable removal does not satisfy
 those separate [administration requirements](ADMIN_PANEL.md). No existing human
 room is used for removal tests, and no database reset is authorized.
+
+Restoring an archived room preserves both archive and closure. Use All rooms in
+both Directory and Archive filters to find a room with both flags.