chore: ESLint config, 61 lint fixes across 22 client files, CLAUDE.md update

- Add ESLint v9 flat config with typescript-eslint
- Fix no-floating-promises, no-unused-vars, consistent-return across client
- Refactor livekitSession: delegate entirely to AudioPipeline (1438→1171 lines)
- Add 7 delete-account UI tests in settings-overlay.test.ts
- Update CLAUDE.md with latest features and project structure
- Update .gitignore

.gitignore

@@ -5,6 +5,10 @@ Server/.claude/
 
 # Claude Code skills
 skills/
+\
+
+#github copilot
+.github/
 
 # AI-specific / internal planning docs
 Obsidian-Brain/