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/core-api/package.json

@@ -17,6 +17,7 @@
     "@repo/blog": "workspace:*",
     "@repo/core-shared": "workspace:*",
     "@repo/marketing-pages": "workspace:*",
+    "@repo/media": "workspace:*",
     "@repo/navigation": "workspace:*",
     "@trpc/server": "^11.0.0"
   },