fix: permission checks for speedId and inPort + multi-node IP constraints (#261)

* feat: restrict user permissions and multi-node IP constraints

- Non-admin users cannot set speedId or inPort on forward create/update
- Multi-entrance tunnels disable custom listen IP for forwards
- Multi-exit tunnels disable custom connect IP
- Multi-node hop chains disable custom connect IP per hop
- Remove tunnel-first-IP fallback in forward ingress resolution
- Add contract tests for non-admin permission restrictions

Entire-Checkpoint: 133693290660

* fix: allow non-admin users to submit null speedId and zero inPort

- Backend: Check speedId is not nil before rejecting non-admin requests
- Backend: Only reject inPort if value > 0 for non-admin users
- Frontend: Only include speedId and inPort in payload for admin users
- Tests: Add contract tests for null speedId and zero inPort cases

.entire/metadata/ses_34d1913a5ffe44UcWYV1ea4IGZ/prompt.txt

@@ -0,0 +1,13 @@
+提交全部变更并且push，创建pr合并，发布新tag，beta版本
+
+---
+
+不对，tag是2.1.7-beta2
+
+---
+
+2.1.8-beta1  标签没有被删除成功
+
+---
+
+2.1.8-alpha1  标签没有被删除成功

.entire/metadata/ses_34d1913a5ffe44UcWYV1ea4IGZ/summary.txt

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+已删除 `2.1.8-alpha1` 标签。当前最新版本为 `2.1.7-beta2`。