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>

src/proxy.ts

@@ -29,8 +29,8 @@ export async function proxy(request: NextRequest) {
   }
 
   // ── CLIENT TOKEN GUARD ───────────────────────────────────────────────────
-  if (pathname.startsWith("/c/")) {
-    const tokenMatch = pathname.match(/^\/c\/([a-zA-Z0-9_-]+)/);
+  if (pathname.startsWith("/client/")) {
+    const tokenMatch = pathname.match(/^\/client\/([a-zA-Z0-9_-]+)/);
     if (!tokenMatch) {
       return NextResponse.rewrite(new URL("/not-found", request.url));
     }
@@ -60,5 +60,5 @@ export async function proxy(request: NextRequest) {
 }
 
 export const config = {
-  matcher: ["/admin/:path*", "/c/:path*"],
+  matcher: ["/admin/:path*", "/client/:path*"],
 };