Add proper return type for fetchConnections method

[AlmogCohen]

Summary

Added proper TypeScript return type for the fetchConnections() method to improve type safety and developer experience.

Changes

Added LibreConnectionsResponse interface that properly types the response from the connections endpoint:

export interface LibreConnectionsResponse extends LibreResponse {
  status: number;
  data: LibreConnection[];
  ticket: Ticket;
}

Updated fetchConnections() method to use this type:

public async fetchConnections(): Promise<LibreConnectionsResponse> {
  // ... implementation
  const connections = await this._fetcher<LibreConnectionsResponse>(
    LibreLinkUpEndpoints.Connections, 
    { headers }
  );
  // ...
}

Benefits

1. Type Safety: IDE and TypeScript can now properly infer the return type
2. Better Autocomplete: Developers get proper suggestions when working with connections data
3. Type Checking: Catches potential bugs at compile time
4. Documentation: Type definition serves as inline documentation for the API response structure

Example Usage

const client = new LibreLinkClient({ email: 'user@example.com', password: 'pass' });
await client.login();

const response = await client.fetchConnections();
// response is now properly typed as LibreConnectionsResponse
// IDE knows that response.data is LibreConnection[]
const connections = response.data;
connections.forEach(conn => {
  console.log(conn.firstName, conn.lastName); // Fully typed!
});

Testing

• ✅ All existing tests pass (12 pass, 0 fail)
• ✅ TypeScript compilation successful
• ✅ No breaking changes - purely additive typing