refactor(monorepo): remove root package deps, simplify Dockerfiles

Root package.json no longer a workspace member — no src/, no 38 shared
dependencies. Root is now workspace config with dev tooling only (biome,
drizzle-kit, tsx, typescript).

This means Dockerfiles only need:
- pnpm-workspace.yaml + pnpm-lock.yaml + package.json (workspace config)
- The specific service being built
- Only vendor/ packages that service actually depends on (discord-gateway → discord.js-selfbot-v13)

Before: each Dockerfile copied src/, vendor/*, packages/*, all services/
After: each Dockerfile copies only its service + needed vendor deps

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

pnpm-workspace.yaml

@@ -1,5 +1,4 @@
 packages:
-  - .
   - services/frontend
   - services/backend
   - services/discord-gateway