refactor: migrate interfaces to dedicated directory

Reorganizes TypeScript interfaces into a modular structure:
- Create dedicated interfaces directory with specialized files
- Split interfaces by domain (claims, common, limits, records, user)
- Update imports in endorserServer.ts to use new interface locations
- Replace 'any' types with 'unknown' for better type safety
- Add proper type imports and exports

This improves code organization and maintainability by:
- Centralizing interface definitions
- Reducing file size of endorserServer.ts
- Making interface relationships more explicit
- Improving type safety with stricter types

src/interfaces/user.ts

@@ -0,0 +1,8 @@
+export interface UserInfo {
+  did: string;
+  name: string;
+  publicEncKey: string;
+  registered: boolean;
+  profileImageUrl?: string;
+  nextPublicEncKeyHash?: string;
+}