ci: Add comprehensive CI quality gates

- New ci.yml workflow: rust-format, clippy, rust-test, security-audit, frontend-lint
- rustfmt.toml: strict formatting rules (edition 2021, max_width 100, grouped imports)
- clippy.toml: lint configuration with complexity thresholds
- eslint.config.js: ESLint 9 flat config for TypeScript/React
- build.yml: now only triggers on v* tags (ci.yml handles master/PR)
- package.json: updated lint script for ESLint 9 flat config

Quality gates run on every push to master and every PR:
1. Rust Format Check (cargo fmt --check --all)
2. Clippy Lints (pedantic + deny warnings)
3. Rust Unit Tests (cargo test --workspace --all-features)
4. Security Audit (cargo audit)
5. Frontend Lint (ESLint + TypeScript type check)

frontend/package.json

@@ -7,7 +7,7 @@
     "dev": "vite",
     "build": "tsc && vite build",
     "preview": "vite preview",
-    "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0",
+    "lint": "eslint src/ --ext .ts,.tsx --max-warnings 0",
     "type-check": "tsc --noEmit"
   },
   "dependencies": {