feat: cloud backup destinations + long-term resource history

Cloud backups (Dropbox / WebDAV / SFTP):
- backup-manager.js: save + load handlers per provider, credential
  resolution via credentialManager, destination probe.
- routes/backups.js: /credentials/{provider} (masked GET, POST, DELETE),
  /test-destination, scheduling endpoints.
- status/js/backup-restore.js: destination picker, provider-specific
  credential forms, test button wired to backend probe.
- npm deps already present (dropbox 10.34.0, webdav 5.7.1,
  ssh2-sftp-client 11.0.0).

Resource history:
- resource-monitor.js: three-tier rollup storage — raw 10s samples
  (7-day retention), hourly rollups (30-day), daily rollups
  (365-day). getHistoryByRange() auto-selects the appropriate tier.
- routes/monitoring.js: /monitoring/history/:containerId now supports
  startTime/endTime range mode (legacy ?hours=N still works).
- status/js/resource-monitor.js + dashboard.css: "History" tab with
  range buttons (1h/24h/7d/30d/1y), SVG sparklines for
  CPU / memory / network. Renderer handles raw and rolled-up shapes.

status/dist/features.js rebuilt from source via build.js.

Lifted out of wip/cloud-backups-and-history; the half-finished
app-deps feature from that branch (frontend calls /api/v1/apps/
check-dependencies but the endpoint doesn't exist) is preserved
separately on wip/app-deps for later.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

status/css/dashboard.css

@@ -2815,6 +2815,28 @@ button:focus-visible {
   display: block;
 }
 
+/* Range selector buttons (resource monitor history) */
+.stats-range-btn {
+  padding: 4px 10px;
+  background: var(--card-base);
+  border: 1px solid var(--border);
+  color: var(--muted);
+  border-radius: 4px;
+  font-size: 0.75rem;
+  cursor: pointer;
+}
+
+.stats-range-btn:hover {
+  border-color: var(--accent);
+  color: var(--fg);
+}
+
+.stats-range-btn.active {
+  background: color-mix(in srgb, var(--accent) 18%, transparent);
+  border-color: var(--accent);
+  color: var(--accent);
+}
+
 /* Status badges (Health and Updates) */
 .status-badge {
   display: inline-flex;