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/components/admin/ClientRow.tsx

@@ -56,12 +56,12 @@ export function ClientRow({ client }: { client: ClientWithPayments }) {
       </td>
       <td className="py-3 px-4">
         <a
-          href={`/c/${client.token}`}
+          href={`/client/${client.token}`}
           target="_blank"
           rel="noopener noreferrer"
           className="text-xs text-[#1A463C] hover:underline font-mono"
         >
-          /c/{client.token.slice(0, 8)}…
+          /client/{client.token.slice(0, 8)}…
         </a>
       </td>
     </tr>