feat: drive migration & Tier 2 restic deprecation (v0.18.0)

Phase 1: Deprecate restic as Tier 2 method (rsync only), auto-migrate on startup
Phase 2: Enhanced per-app migration with backup awareness, DB dump copy, auto-cleanup
Phase 3: Full drive migration with decommissioned state, rollback support, wizard UI
Phase 4: Hub report includes decommissioned drive state

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/web/templates/style.css

@@ -2264,7 +2264,12 @@ a.stat-card:hover {
     opacity: 0.75;
     border-style: dashed;
 }
-.storage-disconnected .storage-disconnected-info {
+.storage-decommissioned {
+    opacity: 0.6;
+    border-color: var(--border-color);
+}
+.storage-disconnected .storage-disconnected-info,
+.storage-decommissioned .storage-disconnected-info {
     display: flex;
     flex-direction: column;
     gap: .25rem;