fix: all lint errors, test + lint pre-commit passing

Frontend:
- Split nodeTypes/edgeTypes into separate .ts files (react-refresh)
- Remove setState-in-effect in NodeModal (key prop reset)
- Fix handleSave accessed before declaration (useRef pattern)
- Exclude src/components/ui/** from eslint (shadcn generated)
- Use defineConfig from vitest/config for test type support

Backend:
- ruff --fix: sort imports, datetime.UTC alias
- Raise line-length to 120, ignore E501 in tests
- Break long update_node/update_edge signatures
- pyproject.toml: per-file-ignores for tests

frontend/vite.config.ts

@@ -1,5 +1,5 @@
 import path from 'path'
-import { defineConfig } from 'vite'
+import { defineConfig } from 'vitest/config'
 import react from '@vitejs/plugin-react'
 import tailwindcss from '@tailwindcss/vite'
 
@@ -10,6 +10,16 @@ export default defineConfig({
       '@': path.resolve(__dirname, './src'),
     },
   },
+  test: {
+    environment: 'jsdom',
+    globals: true,
+    setupFiles: ['./src/test/setup.ts'],
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'lcov'],
+      exclude: ['src/components/ui/**', 'src/test/**'],
+    },
+  },
   server: {
     proxy: {
       '/api': 'http://localhost:8000',