118-elementsynapse: install suppress_redactions push-rule for @admin

Stops redaction events (Signal disappearing messages, deletes,
etc.) from bumping the mobile notification badge in the
future.

containers/118-elementsynapse.md

@@ -53,7 +53,14 @@ Fix (after stopping Synapse and backing up `homeserver.db`):
 - `DELETE FROM event_push_actions WHERE event_id IN (SELECT event_id FROM events WHERE type='m.room.redaction')` — removes redaction-driven notifications.
 - Rebuild `event_push_summary` from the remaining rows (preserve `thread_id='main'` to satisfy the NOT-NULL check constraint).
 
-Result: 125 → 4 (legitimate WhatsApp unreads). If this recurs, the durable fix is a push-rule to suppress `m.room.redaction` notifications (account data, per-user) or upstream a custom rule in `homeserver.yaml`.
+Result: 125 → 4 (legitimate WhatsApp unreads).
+
+Then, to stop this recurring, an **override push-rule** was installed for `@admin` via the client API:
+```
+PUT /_matrix/client/v3/pushrules/global/override/suppress_redactions
+{ "actions": [], "conditions": [{ "kind": "event_match", "key": "type", "pattern": "m.room.redaction" }] }
+```
+With empty `actions`, all `m.room.redaction` events are silently ignored by the push system. Inspect/remove via the same endpoint. (Note: rule ids beginning with `.` are reserved for server defaults — custom ids cannot start with a dot.)
 
 ### 2026-05-15 — disk-full incident, rootfs grown to 16 GiB, bridges restarted
 Element/Synapse was unreliable for ~2 days: messages dropping, sync requests stalling, mautrix bridges (slack/signal/meta/linkedin/whatsapp) all exited around 2026-05-13. Root cause: rootfs reached 100% (19 MB free of 7.8 G); Synapse logs showed `OSError: [Errno 28] No space left on device` during flush. Fix: `pct resize 118 rootfs +8G` (host `pve` VG had plenty of headroom), `journalctl --vacuum-size=50M` to recover ~200 M, `systemctl restart matrix-synapse`, then `docker compose up -d` in each `/root/mautrix-*` directory. Also expanded this wiki page to document the bridges, synapse-admin, and the actual DB backend (Postgres, not the SQLite leftover).