feat(media): full Clean Architecture scaffold

Media is now a complete vertical-feature package mirroring auth/blog
structure: entities (models + errors), application (repositories +
use-cases), infrastructure (real Payload-backed + mock siblings),
interface-adapters (per-use-case controllers), DI (symbols + module +
container + bind-production), integrations/api (mediaRouter), factory,
contract suite, and feature integration tests.

Wired into:
- packages/core-api/src/root.ts (added `media: mediaRouter`)
- apps/web-next/src/server/bind-production.ts (calls bindProductionMedia)
- tsconfig.base.json (added @repo/media/api and ./di/bind-production aliases)

56 new tests in @repo/media (13 test files); core-api router test updated
to assert media. procedures. All 26 turbo tasks green.

Refactor log: §2, §4.1, §4.2, §5.1, §6.1
Spec: §6.5

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

packages/media/src/di/symbols.ts

@@ -0,0 +1,11 @@
+export const MEDIA_SYMBOLS = {
+  IMediaRepository: Symbol.for("media:IMediaRepository"),
+  // Use cases
+  IGetMediaUseCase: Symbol.for("media:IGetMediaUseCase"),
+  IListMediaUseCase: Symbol.for("media:IListMediaUseCase"),
+  IDeleteMediaUseCase: Symbol.for("media:IDeleteMediaUseCase"),
+  // Controllers
+  IGetMediaController: Symbol.for("media:IGetMediaController"),
+  IListMediaController: Symbol.for("media:IListMediaController"),
+  IDeleteMediaController: Symbol.for("media:IDeleteMediaController"),
+} as const;