Phase 3: env masking, image updates, port conflicts, resources, templates (0.3.0)

Backend:
- update_service: registry manifest digest check (Docker Hub/ghcr/lscr/private
  v2 token auth) vs local RepoDigests; in-memory cache + background loop
- port_service: parse compose ports, check /proc/net/tcp[6] + docker bindings
- template_service + bundled templates (jellyfin/vaultwarden/uptime-kuma/
  paperless-ngx/gitea) with {{VAR}} placeholders; custom templates in DB
- compose_edit set_resources (deploy.resources.limits/reservations)
- routers: images, ports, templates, editor/set-resources
- Template model; background update task wired into lifespan

Frontend:
- EnvEditor (table + raw, sensitive masking, quick-insert)
- Images page + UpdateBadge + dashboard 'updates available' banner
- PortConflictDialog pre-deploy check on Deploy
- ResourcePanel (CPU/RAM sliders) as editor Limits tab
- Templates page with per-variable instantiate form

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/stacks/EditorHelperPanel.tsx

@@ -1,13 +1,14 @@
 import { useEffect, useState } from "react";
-import { RefreshCw, HardDrive, Cpu, Plug } from "lucide-react";
+import { RefreshCw, HardDrive, Cpu, Plug, Gauge } from "lucide-react";
 import { VolumeWizard } from "@/components/volumes/VolumeWizard";
 import { GPUSelector } from "@/components/gpu/GPUSelector";
 import { DevicePanel } from "@/components/gpu/DevicePanel";
+import { ResourcePanel } from "@/components/stacks/ResourcePanel";
 import { editorApi } from "@/api/editor";
 import { apiErrorMessage } from "@/api/client";
 import { toast } from "sonner";
 
-type Tab = "volumes" | "gpu" | "devices";
+type Tab = "volumes" | "gpu" | "devices" | "resources";
 
 export function EditorHelperPanel({
   yaml,
@@ -83,6 +84,7 @@ export function EditorHelperPanel({
           ["volumes", "Volumes", HardDrive],
           ["gpu", "GPU", Cpu],
           ["devices", "Devices", Plug],
+          ["resources", "Limits", Gauge],
         ] as [Tab, string, typeof Cpu][]).map(([id, label, Icon]) => (
           <button
             key={id}
@@ -130,6 +132,14 @@ export function EditorHelperPanel({
             }}
           />
         )}
+        {tab === "resources" && (
+          <ResourcePanel
+            onApply={(res) => {
+              if (!guard()) return;
+              run(() => editorApi.setResources(yaml, service, res));
+            }}
+          />
+        )}
       </div>
     </div>
   );