chore: add GitHub automation and fix rand vulnerability

GitHub Actions:
- Add Dependabot for weekly dependency updates (cargo, github-actions)
- Add PR labeler workflow with file-based auto-labeling
- Add issue/PR templates (bug report, feature request, PR template)
- Fix release.yml artifact paths and labeler.yml config syntax
Security:
- Upgrade rand 0.8 → 0.10 to fix RUSTSEC-2026-0097 unsoundness
- Update screenshot.rs for rand 0.10 API (thread_rng → rng, gen_range → random_range)

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,12 @@
+# Feature Request
+
+**Is your feature request related to a problem? Please describe.**
+
+
+**Describe the solution you'd like**
+
+
+**Describe alternatives you've considered**
+
+
+**Additional context**