refactor(shared): extract hasWriteAll(locals) permission helper

The locals.user.groups.some(...WRITE_ALL) derivation was copy-pasted across
the persons directory, persons review and the two document loaders touched by
this PR. Extract a single tested hasWriteAll(locals) helper in
$lib/shared/server and reuse it, removing the ad-hoc casts.

Refs #667

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/lib/shared/server/permissions.spec.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest';
+import { hasWriteAll } from './permissions';
+
+type Locals = { user?: { groups?: { permissions: string[] }[] } };
+
+const localsWith = (permissions: string[][]): Locals => ({
+	user: { groups: permissions.map((p) => ({ permissions: p })) }
+});
+
+describe('hasWriteAll', () => {
+	it('returns true when a group grants WRITE_ALL', () => {
+		expect(hasWriteAll(localsWith([['READ_ALL', 'WRITE_ALL']]))).toBe(true);
+	});
+
+	it('returns true when WRITE_ALL is in any of several groups', () => {
+		expect(hasWriteAll(localsWith([['READ_ALL'], ['WRITE_ALL']]))).toBe(true);
+	});
+
+	it('returns false when no group grants WRITE_ALL', () => {
+		expect(hasWriteAll(localsWith([['READ_ALL'], ['ANNOTATE_ALL']]))).toBe(false);
+	});
+
+	it('returns false for an anonymous user (no locals.user)', () => {
+		expect(hasWriteAll({})).toBe(false);
+	});
+
+	it('returns false when the user has no groups', () => {
+		expect(hasWriteAll({ user: {} })).toBe(false);
+	});
+});

frontend/src/lib/shared/server/permissions.ts

@@ -0,0 +1,14 @@
+/**
+ * Server-side permission predicates derived from the authenticated user in `locals`.
+ *
+ * The user shape is intentionally narrowed to the only field these checks read
+ * (`groups[].permissions`) so the helper works against `App.Locals` without importing it.
+ */
+type PermissionLocals = {
+	user?: { groups?: { permissions: string[] }[] } | null;
+};
+
+/** True when any of the user's groups grants WRITE_ALL. False for anonymous users. */
+export function hasWriteAll(locals: PermissionLocals): boolean {
+	return locals.user?.groups?.some((group) => group.permissions.includes('WRITE_ALL')) ?? false;
+}

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

@@ -2,6 +2,7 @@ import { error, fail, redirect } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
 import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { parseBackendError, getErrorMessage } from '$lib/shared/errors';
+import { hasWriteAll } from '$lib/shared/server/permissions';
 
 export async function load({
 	params,
@@ -15,11 +16,7 @@ export async function load({
 	depends: (dep: string) => void;
 }) {
 	depends('app:document');
-	const canWrite =
-		locals.user?.groups?.some((g: { permissions: string[] }) =>
-			g.permissions.includes('WRITE_ALL')
-		) ?? false;
-	if (!canWrite) throw error(403, 'Forbidden');
+	if (!hasWriteAll(locals)) throw error(403, 'Forbidden');
 
 	const { id } = params;
 	const api = createApiClient(fetch);

frontend/src/routes/documents/new/+page.server.ts

@@ -2,6 +2,7 @@ import { fail, redirect } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
 import { createApiClient } from '$lib/shared/api.server';
 import { parseBackendError, getErrorMessage } from '$lib/shared/errors';
+import { hasWriteAll } from '$lib/shared/server/permissions';
 
 export async function load({
 	fetch,
@@ -12,11 +13,7 @@ export async function load({
 	locals: App.Locals;
 	url: URL;
 }) {
-	const canWrite =
-		locals.user?.groups?.some((g: { permissions: string[] }) =>
-			g.permissions.includes('WRITE_ALL')
-		) ?? false;
-	if (!canWrite) throw redirect(303, '/');
+	if (!hasWriteAll(locals)) throw redirect(303, '/');
 
 	const senderId = url.searchParams.get('senderId') || '';
 	const receiverId = url.searchParams.get('receiverId') || '';

frontend/src/routes/persons/+page.server.ts

@@ -1,6 +1,7 @@
 import { error } from '@sveltejs/kit';
 import { createApiClient } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
+import { hasWriteAll } from '$lib/shared/server/permissions';
 
 const PAGE_SIZE = 50;
 
@@ -21,10 +22,7 @@ export async function load({ url, fetch, locals }) {
 
 	const api = createApiClient(fetch);
 
-	const canWrite =
-		(locals.user as { groups?: { permissions: string[] }[] } | undefined)?.groups?.some((g) =>
-			g.permissions.includes('WRITE_ALL')
-		) ?? false;
+	const canWrite = hasWriteAll(locals);
 
 	const filters = {
 		q: q || undefined,

frontend/src/routes/persons/review/+page.server.ts

@@ -1,14 +1,12 @@
 import { error, fail } from '@sveltejs/kit';
 import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
+import { hasWriteAll } from '$lib/shared/server/permissions';
 
 const PAGE_SIZE = 50;
 
 export async function load({ url, fetch, locals }) {
-	const canWrite =
-		(locals.user as { groups?: { permissions: string[] }[] } | undefined)?.groups?.some((g) =>
-			g.permissions.includes('WRITE_ALL')
-		) ?? false;
+	const canWrite = hasWriteAll(locals);
 
 	const page = Math.max(0, Number.parseInt(url.searchParams.get('page') ?? '0', 10) || 0);
 	const api = createApiClient(fetch);