test: Add minimal UT infrastructure and fix Issue #227

This commit sets up a minimal, KISS-principle testing infrastructure
for both backend and frontend, and includes the fix for Issue #227.

Backend Changes:
- Add Makefile with test commands (test, test-backend, test-frontend, test-coverage)
- Add example test: config/database_test.go
- Fix Go 1.25 printf format string warnings in trader/auto_trader.go
  (Changed log.Printf to log.Print for non-format strings)
- All backend tests pass ✓

Frontend Changes:
- Add Vitest configuration: web/vitest.config.ts (minimal setup)
- Add test utilities: web/src/test/test-utils.tsx
- Add example test: web/src/App.test.tsx
- Add dependencies: vitest, jsdom, @testing-library/react
- All frontend tests pass ✓

Issue #227 Fix:
- Fix AITradersPage to allow editing traders with disabled models/exchanges
- Change validation to use allModels/allExchanges instead of enabledModels/enabledExchanges
- Add comprehensive tests in web/src/components/AITradersPage.test.tsx
- Fixes: https://github.com/tinkle-community/nofx/issues/227

CI/CD:
- Add GitHub Actions workflow: .github/workflows/test.yml
- Non-blocking tests (continue-on-error: true)
- Runs on push/PR to main and dev branches

Test Results:
- Backend: 1 test passing
- Frontend: 5 tests passing (including 4 for Issue #227)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: tinkle-community <tinklefund@gmail.com>

web/package.json

@@ -5,7 +5,8 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc && vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest run"
   },
   "dependencies": {
     "@radix-ui/react-slot": "^1.2.3",
@@ -22,13 +23,16 @@
     "zustand": "^5.0.2"
   },
   "devDependencies": {
+    "@testing-library/react": "^16.1.0",
     "@types/react": "^18.3.17",
     "@types/react-dom": "^18.3.5",
     "@vitejs/plugin-react": "^4.3.4",
     "autoprefixer": "^10.4.20",
+    "jsdom": "^25.0.1",
     "postcss": "^8.4.49",
     "tailwindcss": "^3.4.17",
     "typescript": "^5.8.3",
-    "vite": "^6.0.7"
+    "vite": "^6.0.7",
+    "vitest": "^2.1.8"
   }
 }