Fix Foundry auth: migrate to Better Auth adapter, fix access token retrieval

- Remove @ts-nocheck from better-auth.ts, auth-user/index.ts, app-shell.ts
  and fix all type errors
- Fix getAccessTokenForSession: read GitHub token directly from account
  record instead of calling Better Auth's internal /get-access-token
  endpoint which returns 403 on server-side calls
- Re-implement workspaceAuth helper functions (workspaceAuthColumn,
  normalizeAuthValue, workspaceAuthClause, workspaceAuthWhere) that were
  accidentally deleted
- Remove all retry logic (withRetries, isRetryableAppActorError)
- Implement CORS origin allowlist from configured environment
- Document cachedAppWorkspace singleton pattern
- Add inline org sync fallback in buildAppSnapshot for post-OAuth flow
- Add no-retry rule to CLAUDE.md

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

foundry/packages/frontend/src/components/mock-onboarding.tsx

@@ -56,7 +56,11 @@ function DesktopDragRegion() {
   const isDesktop = !!import.meta.env.VITE_DESKTOP;
   const onDragMouseDown = useCallback((event: React.PointerEvent) => {
     if (event.button !== 0) return;
-    const ipc = (window as Record<string, unknown>).__TAURI_INTERNALS__ as { invoke: (cmd: string, args?: unknown) => Promise<unknown> } | undefined;
+    const ipc = (window as unknown as Record<string, unknown>).__TAURI_INTERNALS__ as
+      | {
+          invoke: (cmd: string, args?: unknown) => Promise<unknown>;
+        }
+      | undefined;
     if (ipc?.invoke) {
       ipc.invoke("plugin:window|start_dragging").catch(() => {});
     }