feat(proxy): add proxy IP management and account routing

Add admin CRUD and connectivity checks for SOCKS5/SOCKS5H proxy nodes.

Allow accounts to bind to a proxy, route DeepSeek requests through the selected node, and expose proxy management in the admin UI.

AGENTS.md

@@ -0,0 +1,22 @@
+# AGENTS.md
+
+These rules apply to all agent-made changes in this repository.
+
+## PR Gate
+
+- Before opening or updating a PR, run the same local gates as `.github/workflows/quality-gates.yml`.
+- Required commands:
+  - `./tests/scripts/check-refactor-line-gate.sh`
+  - `./tests/scripts/run-unit-all.sh`
+  - `npm run build --prefix webui`
+
+## Go Lint Rules
+
+- Run `gofmt -w` on every changed Go file before commit or push.
+- Do not ignore error returns from I/O-style cleanup calls such as `Close`, `Flush`, `Sync`, or similar methods.
+- If a cleanup error cannot be returned, log it explicitly.
+
+## Change Scope
+
+- Keep changes additive and tightly scoped to the requested feature or bugfix.
+- Do not mix unrelated refactors into feature PRs unless they are required to make the change pass gates.