Fix auth errors, CORS, control center login, and stale session handling

- Mitra auth: parse DioException response for proper error messages
  (ACCOUNT_NOT_FOUND, ACCOUNT_INACTIVE) instead of generic "OTP invalid"
- Backend: add CORS to internal app (port 3001) for control center
- Control center: fix login race condition (wait for AuthContext verify
  before navigating), fix MitraActivityPage fetching paginated data
- Stale session goodbye: both apps detect SESSION_NOT_ACTIVE/409 and
  move to complete state instead of retrying endlessly

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/app.internal.js

@@ -1,4 +1,5 @@
 import Fastify from 'fastify'
+import cors from '@fastify/cors'
 import sensible from '@fastify/sensible'
 import { mitraManagementRoutes } from './routes/internal/mitra.routes.js'
 import { ccUserRoutes } from './routes/internal/cc-user.routes.js'
@@ -12,6 +13,7 @@ import { errorHandler } from './plugins/error-handler.js'
 export const buildInternalApp = async () => {
   const app = Fastify({ logger: true })
 
+  await app.register(cors, { origin: true })
   await app.register(sensible)
   app.setErrorHandler(errorHandler)