docs: consolidate restore documentation into ops/restore-tests

- merge RESTORE_HANDBOOK.md into ops/restore-tests/README.md (single
  operations doc; restore status lives only in RESTORE_MATRIX maturity
  table)
- RESTORE_MATRIX.md: extract embedded runbook drafts (261 -> 141 lines);
  unraid-flash and tailscale stubs become ops/restore-tests runbooks,
  adguard/redis checklists superseded by validated scripts
- delete six historical pre-first-run *-plan.md files (runbook + script
  are the source of truth since the validated first runs)
- SERVICES_RECOVERY: drop completed task table; DISASTER_RECOVERY:
  point related docs and section 11 to MASTER_TODO/schedule

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ops/restore-tests/immich-runbook.md

@@ -34,7 +34,6 @@ Vor dem ersten Lauf muss Operator entscheiden:
   - `ops/restore-tests/immich-compose.test.yml`
   - `ops/restore-tests/immich-restore-test.sh`
   - `ops/restore-tests/immich-restore-test.ps1` (Scaffold, kein Live-Run)
-  - `ops/restore-tests/immich-plan.md`
   - `ops/restore-tests/immich-runbook.md`
 
 ## Erster Lauf - trockene Variante