chore(github): overhaul issue and PR templates

Bug, feature, and question templates now collect the triage signal the
maintainers usually have to ask for (install method, OS, area, reverse
proxy, logs, version). config.yml disables blank issues and points to
Wiki / existing issues / latest release from the picker.

PR template adds Summary/Why/Type/Areas/Testing/Breaking-changes
sections and a fuller checklist (build, tests, lint, typecheck, docs).
Renamed pull_request_template.yml -> .md to match GitHub's conventional
extension; the old .yml was being read as markdown anyway.

.github/pull_request_template.md

@@ -0,0 +1,63 @@
+## Summary
+
+<!-- What does this PR do? One or two sentences. -->
+
+## Why
+
+<!--
+What problem does this solve, or what use case does it enable?
+Link related issues here: "Closes #123", "Refs #456".
+-->
+
+## Type of change
+
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactoring (no behavior change)
+- [ ] Documentation
+- [ ] Tests only
+- [ ] Build / CI / tooling
+- [ ] Other
+
+## Areas affected
+
+- [ ] Frontend (UI / panel pages)
+- [ ] Backend (API endpoints, login, settings)
+- [ ] Xray config generation
+- [ ] Subscription (share links / Clash / JSON)
+- [ ] Statistics / traffic counters
+- [ ] Database / migrations
+- [ ] Install / upgrade script
+- [ ] Docker image
+- [ ] Multi-node (sub-nodes)
+- [ ] Telegram bot
+
+## How was this tested?
+
+<!--
+Concrete steps the reviewer can repeat. For UI changes: which page,
+which actions, which browser. For backend: which endpoint, which payload,
+which response. Mention any new unit/integration tests added.
+-->
+
+## Screenshots / recordings
+
+<!-- Required for UI changes. Drag images or GIFs here. Remove if N/A. -->
+
+## Breaking changes
+
+<!--
+Does this change require existing users to update their config, run a
+migration, or change their API calls? If yes, describe the migration path.
+Write "None" if there are no breaking changes.
+-->
+
+## Checklist
+
+- [ ] I tested the change locally and confirmed the described behavior.
+- [ ] I added or updated tests for the new behavior (when applicable).
+- [ ] `go build ./...` and the test suite pass locally.
+- [ ] For frontend changes: `npm run lint`, `npm run typecheck`, and `npm run build` pass.
+- [ ] I updated the Wiki / README / API docs if user-facing behavior changed.
+- [ ] My commits follow the project's existing message style.
+- [ ] I have no unrelated changes mixed into this PR.