infra(04-00): route /c/ → /client/, Dockerfile, Gitea deploy

- Rename src/app/c/[token] → src/app/client/[token]
- Update proxy.ts, ClientRow, admin client detail with /client/ path
- Add output: "standalone" to next.config.ts for Docker build
- Add Dockerfile (multi-stage, node:20-alpine) and .dockerignore
- Push schema to Coolify Postgres via SSH tunnel (drizzle-kit push ✓)
- Update CLAUDE.md constraint 4 to reflect /client/ route
- Add Phase 4 planning artifacts (04-00, 04-RESEARCH, 04-PATTERNS)

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

next.config.ts

@@ -1,7 +1,7 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
 };
 
 export default nextConfig;