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/conversations/+page.server.ts

@@ -2,61 +2,63 @@ import type { components } from '$lib/generated/api';
 import { createApiClient } from '$lib/api.server';
 
 export async function load({ url, fetch }) {
-    const senderId = url.searchParams.get('senderId') || '';
-    const receiverId = url.searchParams.get('receiverId') || '';
-    const from = url.searchParams.get('from') || '';
-    const to = url.searchParams.get('to') || '';
-    const dir = url.searchParams.get('dir') || 'DESC';
+	const senderId = url.searchParams.get('senderId') || '';
+	const receiverId = url.searchParams.get('receiverId') || '';
+	const from = url.searchParams.get('from') || '';
+	const to = url.searchParams.get('to') || '';
+	const dir = url.searchParams.get('dir') || 'DESC';
 
-    const api = createApiClient(fetch);
+	const api = createApiClient(fetch);
 
-    let documents: components['schemas']['Document'][] = [];
-    let senderName = '';
-    let receiverName = '';
+	let documents: components['schemas']['Document'][] = [];
+	let senderName = '';
+	let receiverName = '';
 
-    const requests: Promise<void>[] = [];
+	const requests: Promise<void>[] = [];
 
-    if (senderId && receiverId) {
-        requests.push(
-            api.GET('/api/documents/conversation', {
-                params: {
-                    query: {
-                        senderId,
-                        receiverId,
-                        dir,
-                        from: from || undefined,
-                        to: to || undefined
-                    }
-                }
-            }).then(({ data }) => { documents = data ?? []; })
-        );
-    }
+	if (senderId && receiverId) {
+		requests.push(
+			api
+				.GET('/api/documents/conversation', {
+					params: {
+						query: {
+							senderId,
+							receiverId,
+							dir,
+							from: from || undefined,
+							to: to || undefined
+						}
+					}
+				})
+				.then(({ data }) => {
+					documents = data ?? [];
+				})
+		);
+	}
 
-    if (senderId) {
-        requests.push(
-            api.GET('/api/persons/{id}', { params: { path: { id: senderId } } })
-                .then(({ data }) => {
-                    const p = data as { firstName: string; lastName: string } | undefined;
-                    if (p) senderName = `${p.firstName} ${p.lastName}`;
-                })
-        );
-    }
+	if (senderId) {
+		requests.push(
+			api.GET('/api/persons/{id}', { params: { path: { id: senderId } } }).then(({ data }) => {
+				const p = data as { firstName: string; lastName: string } | undefined;
+				if (p) senderName = `${p.firstName} ${p.lastName}`;
+			})
+		);
+	}
 
-    if (receiverId) {
-        requests.push(
-            api.GET('/api/persons/{id}', { params: { path: { id: receiverId } } })
-                .then(({ data }) => {
-                    const p = data as { firstName: string; lastName: string } | undefined;
-                    if (p) receiverName = `${p.firstName} ${p.lastName}`;
-                })
-        );
-    }
+	if (receiverId) {
+		requests.push(
+			api.GET('/api/persons/{id}', { params: { path: { id: receiverId } } }).then(({ data }) => {
+				const p = data as { firstName: string; lastName: string } | undefined;
+				if (p) receiverName = `${p.firstName} ${p.lastName}`;
+			})
+		);
+	}
 
-    await Promise.all(requests);
+	await Promise.all(requests);
 
-    return {
-        documents,
-        initialValues: { senderName, receiverName },
-        filters: { senderId, receiverId, from, to, dir }
-    };
+	return {
+		documents,
+		initialValues: { senderName, receiverName },
+		filters: { senderId, receiverId, from, to, dir }
+	};
 }