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/common.ts

@@ -0,0 +1,41 @@
+// similar to VerifiableCredentialSubject... maybe rename this
+export interface GenericVerifiableCredential {
+  "@context"?: string;
+  "@type": string;
+  [key: string]: unknown;
+}
+
+export interface GenericCredWrapper<T extends GenericVerifiableCredential> {
+  claim: T;
+  claimType?: string;
+  handleId: string;
+  id: string;
+  issuedAt: string;
+  issuer: string;
+  publicUrls?: Record<string, string>;
+}
+
+export interface ResultWithType {
+  type: string;
+}
+
+export interface SuccessResult extends ResultWithType {
+  type: "success";
+  response: unknown;
+}
+
+export interface ErrorResponse {
+  error?: {
+    message?: string;
+  };
+}
+
+export interface InternalError {
+  error: string;
+  userMessage?: string;
+}
+
+export interface ErrorResult extends ResultWithType {
+  type: "error";
+  error: InternalError;
+}