fix(xray): sync routing rules when outbound tag is renamed

[nima1024m]

Summary

• Propagate outbound tag renames to routing rules, balancer selectors/fallbacks, and sockopt dialerProxy references
• Fixes invalid routing rules after renaming an outbound (e.g. To-External-Proxy) in the Outbounds tab
• Adds .cursor/ to .gitignore for local-only editor files

Why

Editing an outbound only updated the outbounds array. Routing rules store outboundTag as a plain string, so renaming left rules pointing at a tag that no longer exists. Balancer renames and WARP/Nord outbound resets already updated references; the regular Outbounds edit path did not.

Files affected

• frontend/src/pages/xray/basics/helpers.ts — new propagateOutboundTagRename()
• frontend/src/pages/xray/outbounds/OutboundsTab.tsx — call on outbound edit
• frontend/src/pages/xray/XrayPage.tsx — reuse helper for WARP/Nord path
• frontend/src/test/outbound-tag-rename.test.ts — unit tests
• .gitignore — ignore .cursor/

Test plan

• npx vitest run src/test/outbound-tag-rename.test.ts (4 passed)
• npx tsc --noEmit
• Manual: Xray → Outbounds → rename outbound used by a routing rule → Routing tab shows updated outboundTag → Save → verify config.json

Risks

• Frontend-only change; no backend or migration impact
• Also updates balancer selector/fallbackTag and dialerProxy when those reference the old tag