v0.11.8 — Per-App Cross-Drive Backup (3-2-1 rule)

New feature: backup app data to a secondary storage drive to satisfy
the "different media" requirement of the 3-2-1 backup rule.

- settings.go: CrossDriveBackup struct, AppBackupPrefs.CrossDrive field,
  getter/setter methods, GetOrCreateCrossDrivePassword, preserves
  cross-drive config when toggling nightly backup

- crossdrive.go (new): CrossDriveRunner with rsync and restic backends.
  Validates destination (mount point, writable), prevents source/dest
  overlap, per-app concurrency lock, persists last_run/status/size.

- main.go: wire CrossDriveRunner, register cross-drive-daily (03:30)
  and cross-drive-weekly (04:30 Sundays) scheduler jobs

- router.go: 4 new API endpoints — save config, trigger run, get status,
  run-all. Router now accepts Settings and CrossDriveRunner.

- server.go: Server struct accepts CrossDriveRunner, new web route
  POST /settings/cross-backup/{name}

- handlers.go: deployHandler populates CrossDriveConfig, BackupDestPaths,
  BackupDestWarning, AppBackupEnabled. settingsCrossBackupHandler saves
  config. backupsHandler builds CrossDriveSummary, UnconfiguredApps,
  CrossDriveWarnings for backup page.

- deploy.html: "Biztonsági mentés" card with destination/method/schedule
  dropdowns, last-run status, manual trigger button, flash messages.

- backups.html: "Másolatok másik meghajtóra" section with per-app
  status rows, unconfigured app warnings, "Összes futtatása most" button.

- style.css: margin-bottom fix for .deploy-stale-data, new cross-drive
  card and list styles.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

controller/internal/web/templates/style.css

@@ -2238,6 +2238,7 @@ a.stat-card:hover {
     border-radius: var(--radius);
     padding: 1.5rem;
     margin-top: 1rem;
+    margin-bottom: 1.5rem;
 }
 
 .deploy-stale-data h4 {
@@ -2265,3 +2266,67 @@ a.stat-card:hover {
 .btn-danger:hover {
     opacity: 0.85;
 }
+
+/* Cross-drive backup card on deploy page */
+.deploy-cross-drive {
+    background: var(--card-bg);
+    border: 1px solid var(--border);
+    border-radius: var(--radius);
+    padding: 1.5rem;
+    margin-top: 1rem;
+    margin-bottom: 1rem;
+}
+
+.deploy-cross-drive h4 {
+    margin: 0 0 1rem 0;
+    color: var(--text-primary);
+}
+
+.cross-drive-nightly {
+    margin-bottom: .5rem;
+}
+
+/* Cross-drive list on backup page */
+.cross-drive-list {
+    display: flex;
+    flex-direction: column;
+    gap: .5rem;
+}
+
+.cross-drive-item {
+    background: var(--bg-secondary);
+    border-radius: var(--radius);
+    padding: .75rem 1rem;
+}
+
+.cross-drive-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    flex-wrap: wrap;
+    gap: .5rem;
+}
+
+.cross-drive-name {
+    font-weight: 500;
+    color: var(--text-primary);
+    text-decoration: none;
+}
+
+.cross-drive-name:hover {
+    text-decoration: underline;
+    color: var(--accent-blue);
+}
+
+.cross-drive-meta {
+    display: flex;
+    align-items: center;
+    gap: .4rem;
+    flex-wrap: wrap;
+}
+
+.cross-drive-actions {
+    display: flex;
+    gap: .5rem;
+    flex-wrap: wrap;
+}