feat: add shared @sexy.pivoine.art/types package and fix type safety across frontend/backend

- Create packages/types with shared TypeScript domain model interfaces (User, Video, Model, Article, Comment, Recording, etc.)
- Wire both frontend and backend packages to use @sexy.pivoine.art/types via workspace:*
- Update backend Pothos objectRef types to use shared interfaces instead of inline types
- Update frontend $lib/types.ts to re-export from shared package
- Fix all type errors introduced by more accurate nullable types (avatar/banner as string|null UUIDs, author nullable, events/device_info as object[])
- Add artist_name to comment user select in backend resolver
- Widen utility function signatures (getAssetUrl, getUserInitials, calcReadingTime) to accept null/undefined

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/lib/services.ts

@@ -510,7 +510,7 @@ const UPDATE_PROFILE_MUTATION = gql`
   }
 `;
 
-export async function updateProfile(user: Partial<User>) {
+export async function updateProfile(user: Partial<User> & { password?: string }) {
   return loggedApiCall(
     "updateProfile",
     async () => {
@@ -551,7 +551,7 @@ export async function getStats(fetchFn?: typeof globalThis.fetch) {
 
 // Stub — Directus folder concept dropped
 export async function getFolders(_fetchFn?: typeof globalThis.fetch) {
-  return loggedApiCall("getFolders", async () => []);
+  return loggedApiCall("getFolders", async () => [] as { id: string; name: string }[]);
 }
 
 // ─── Files ───────────────────────────────────────────────────────────────────
@@ -618,6 +618,7 @@ export async function getCommentsForVideo(item: string, fetchFn?: typeof globalT
             id: string;
             first_name: string | null;
             last_name: string | null;
+            artist_name: string | null;
             avatar: string | null;
           } | null;
         }[];