feat(frontend): migrate dashboard projects flow off Supabase to V2 Studio

User-saved projects now read/write through the gateway /v1/saved-projects
(studio schema) using the Identity access-token cookie, replacing the
Supabase `projects` table. Adds src/lib/api/saved-projects.ts client that
maps studio snake_case DTOs into the existing DashboardProject shape.

- DashboardProjectsContent: lists via studio service, degrades gracefully
- /api/projects GET: studio list; POST: copy-from-template create
  (studio requires original_project_id; falls back to scene_data.templateId)
- /api/projects/[projectId] GET/PATCH: proxy to studio with JWT

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/components/dashboard/DashboardProjectsContent.tsx

@@ -1,27 +1,11 @@
 import { DashboardProjectsSection } from "@/components/dashboard/DashboardProjectsSection";
-import { mapProjectRow, type ProjectRow } from "@/lib/projects";
-import { isSupabaseConfigured } from "@/lib/supabase/config";
-import { createClient } from "@/lib/supabase/server";
+import { listSavedProjects } from "@/lib/api/saved-projects";
 
 export async function DashboardProjectsContent() {
-  let projects: ReturnType<typeof mapProjectRow>[] = [];
-
-  if (isSupabaseConfigured()) {
-    const supabase = await createClient();
-    const {
-      data: { user },
-    } = await supabase.auth.getUser();
-
-    const { data } = user
-      ? await supabase
-          .from("projects")
-          .select("*")
-          .eq("user_id", user.id)
-          .order("updated_at", { ascending: false })
-      : { data: [] };
-
-    projects = ((data ?? []) as ProjectRow[]).map(mapProjectRow);
-  }
+  // V2: user-saved projects come from the Studio service via the gateway,
+  // authenticated with the caller's access-token cookie. Degrades to an empty
+  // grid when signed out or the service is unreachable.
+  const projects = await listSavedProjects({ pageSize: 100 });
 
   return <DashboardProjectsSection projects={projects} />;
 }