feat: persistent storage for Deno static sites

- Add storage_enabled and storage_limit_mb columns to static_sites.
- Create/attach Docker volumes (tinyforge-site-{name}-data) for Deno
  sites with storage enabled, mounted at /app/data.
- Grant --allow-write=/app/data in Deno container CMD.
- Add storage usage API endpoint (GET /api/sites/{id}/storage).
- Show storage section in site detail page with usage bar.
- Add storage toggle and limit field to new site wizard.
- Use ConfirmDialog for secret deletion instead of inline delete.

internal/staticsite/deno/template.go

@@ -231,15 +231,19 @@ COPY public/ /app/public/
 COPY api/ /app/api/
 COPY router.ts /app/router.ts
 
+# Create data directory for persistent storage (mounted as volume when enabled).
+RUN mkdir -p /app/data
+
 # Cache dependencies.
 RUN deno install --entrypoint router.ts
 
 EXPOSE 8000
 
-CMD ["deno", "run", "--allow-net", "--allow-read", "--allow-env", "router.ts"]
+CMD ["deno", "run", "--allow-net", "--allow-read", "--allow-write=/app/data", "--allow-env", "router.ts"]
 `
 }
 
+
 // GenerateStaticDockerfile generates a minimal nginx Dockerfile for pure static sites.
 func GenerateStaticDockerfile() string {
 	return `FROM nginx:alpine