* fix(tunnel): validate entry port conflicts before adding new entry nodes
- Add validateTunnelEntryPortConflictsForNewEntries to check cross-tunnel
port conflicts when adding new entry nodes to a tunnel
- Move validation before tx.Commit() to prevent partial success state
- Add contract test for issue #313 regression
- Update panel backend address description to note CDN/HTTPS support
Entire-Checkpoint: eb85eb0c9f2a
* fix: use single quotes to escape Chinese quotation marks in description
sagit