refactor: simplify JNI bridge by delegating to unified service layer

Remove duplicated RPC implementation (light-client-lib/src/rpc.rs, 1112 lines)
and rewrite JNI bridge to use the service layer from PR #270.

- Delete rpc.rs that duplicated all business logic from service/impls.rs
- Rewrite jni_bridge/rpc_handler.rs to delegate to LightClientChainService
  and LightClientNetworkService instead of manually building responses
- Rewrite jni_bridge/query.rs to use service layer, implementing all
  previously TODO methods (get_cells, get_transactions, get_cells_capacity,
  send_transaction, get_transaction, fetch_transaction, estimate_cycles)
- Add service factory functions to jni_bridge/types.rs

Author: eval-exec