fix(frontend): enforce lint locally and in CI, fix all pre-existing violations

## Pre-commit hook
- Add .husky/pre-commit at repo root: runs `cd frontend && npm run lint`
- Update prepare script in package.json to auto-configure git hooks path
  on npm install (git -C .. config core.hooksPath .husky)
- Add lint step to CI unit-tests job so it catches issues before tests run
- Add generated dirs to .prettierignore (paraglide_bak*, test-results, .auth)
- Add src/lib/paraglide_bak* to .gitignore so ESLint can ignore them

## ESLint fixes (all pre-existing)
- Disable svelte/no-navigation-without-resolve: false positive in SvelteKit
  (rule targets Svelte 5 standalone routing, not SvelteKit <a href>)
- Fix svelte/require-each-key: add (item.id)/(item) keys to all {#each} blocks
  across 10 files — improves Svelte reconciliation performance
- Fix svelte/prefer-writable-derived in PersonTypeahead: $state+$effect → $derived
- Fix svelte/prefer-svelte-reactivity: URLSearchParams → SvelteURLSearchParams,
  Map → SvelteMap (enables Svelte reactive tracking)
- Fix @typescript-eslint/no-unused-vars: remove dead imports/variables

## Prettier
- Run npm run format to bring all source files in line with .prettierrc

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/vite.config.ts

@@ -8,7 +8,7 @@ import { sveltekit } from '@sveltejs/kit/vite';
 export default defineConfig({
 	server: {
 		host: '0.0.0.0', // Erlaubt Zugriff von außen
-		port: 5173,      // Standard SvelteKit Port
+		port: 5173, // Standard SvelteKit Port
 		// Proxy für API-Aufrufe während der Entwicklung (Browser -> Vite -> Spring Boot)
 		proxy: {
 			'/api': {
@@ -37,8 +37,8 @@ export default defineConfig({
 						enabled: true,
 						provider: playwright(),
 						instances: [{ browser: 'chromium', headless: true }],
-				screenshotDirectory: 'test-results/screenshots',
-				screenshotFailures: true
+						screenshotDirectory: 'test-results/screenshots',
+						screenshotFailures: true
 					},
 					include: ['src/**/*.svelte.{test,spec}.{js,ts}'],
 					exclude: ['src/lib/server/**']