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/src/routes/documents/[id]/+page.server.ts

@@ -3,17 +3,17 @@ import { createApiClient } from '$lib/api.server';
 import { getErrorMessage } from '$lib/errors';
 
 export async function load({ params, fetch }) {
-    const { id } = params;
-    const api = createApiClient(fetch);
+	const { id } = params;
+	const api = createApiClient(fetch);
 
-    const result = await api.GET('/api/documents/{id}', { params: { path: { id } } });
+	const result = await api.GET('/api/documents/{id}', { params: { path: { id } } });
 
-    if (result.response.status === 401) throw redirect(302, '/login');
+	if (result.response.status === 401) throw redirect(302, '/login');
 
-    if (!result.response.ok) {
-        const code = (result.error as unknown as { code?: string })?.code;
-        throw error(result.response.status, getErrorMessage(code));
-    }
+	if (!result.response.ok) {
+		const code = (result.error as unknown as { code?: string })?.code;
+		throw error(result.response.status, getErrorMessage(code));
+	}
 
-    return { document: result.data! };
+	return { document: result.data! };
 }