feat: add shared API utilities for handling requests and responses

- Introduced `shared.ts` with utility functions for API interactions, including JSON parsing, error handling, and content disposition parsing.
- Added `vault.ts` to manage vault-related operations such as folder and cipher management, including creation, deletion, and bulk operations.
- Implemented encryption and decryption methods for secure data handling within the vault.
- Created `backup-settings-repair.ts` to automatically repair backup settings for admin profiles if needed.

webapp/src/lib/api/shared.ts

@@ -0,0 +1,60 @@
+import { t } from '../i18n';
+import type { SessionState, TokenError } from '../types';
+
+export type AuthedFetch = (input: string, init?: RequestInit) => Promise<Response>;
+export type SessionSetter = (next: SessionState | null) => void;
+
+export const BULK_API_CHUNK_SIZE = 200;
+
+export function chunkArray<T>(items: T[], size: number): T[][] {
+  if (items.length <= size) return [items];
+  const chunks: T[][] = [];
+  for (let i = 0; i < items.length; i += size) {
+    chunks.push(items.slice(i, i + size));
+  }
+  return chunks;
+}
+
+export async function parseJson<T>(response: Response): Promise<T | null> {
+  const text = await response.text();
+  if (!text) return null;
+  try {
+    return JSON.parse(text) as T;
+  } catch {
+    return null;
+  }
+}
+
+export function parseContentDispositionFileName(response: Response, fallback: string): string {
+  const header = String(response.headers.get('Content-Disposition') || '').trim();
+  if (!header) return fallback;
+
+  const utf8Match = header.match(/filename\*\s*=\s*UTF-8''([^;]+)/i);
+  if (utf8Match?.[1]) {
+    try {
+      return decodeURIComponent(utf8Match[1]);
+    } catch {
+      // Ignore malformed filename*= values and fall back to the plain filename.
+    }
+  }
+
+  const plainMatch = header.match(/filename\s*=\s*"([^"]+)"|filename\s*=\s*([^;]+)/i);
+  const raw = plainMatch?.[1] || plainMatch?.[2] || '';
+  const normalized = String(raw).trim().replace(/^"+|"+$/g, '');
+  return normalized || fallback;
+}
+
+export async function parseErrorMessage(resp: Response, fallback: string): Promise<string> {
+  const body = await parseJson<TokenError>(resp);
+  return body?.error_description || body?.error || fallback;
+}
+
+export function createApiError(message: string, status?: number): Error & { status?: number } {
+  const error = new Error(message) as Error & { status?: number };
+  if (status !== undefined) error.status = status;
+  return error;
+}
+
+export function requiredError(messageKey: string): never {
+  throw new Error(t(messageKey));
+}