fix: re-raise HTTPException in RequestLoggingMiddleware

The middleware was catching all exceptions including HTTPException
and returning a generic 503 'Internal server error', masking the real
error details. Added 'except HTTPException: raise' before the generic
except block so HTTPExceptions propagate correctly with their original
status code and detail message.

Also removed debug logging from leave_island handler.

apps/blockchain-node/src/aitbc_chain/app.py

@@ -5,7 +5,7 @@ import os
 import time
 from collections import defaultdict
 from contextlib import asynccontextmanager
-from fastapi import APIRouter, FastAPI, Request
+from fastapi import APIRouter, FastAPI, HTTPException, Request
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse, PlainTextResponse
 from starlette.middleware.base import BaseHTTPMiddleware
@@ -85,6 +85,8 @@ class RequestLoggingMiddleware(BaseHTTPMiddleware):
             elif response.status_code >= 400:
                 metrics_registry.increment("rpc_client_errors_total")
             return response
+        except HTTPException:
+            raise
         except Exception as exc:
             duration = time.perf_counter() - start
             metrics_registry.increment("rpc_unhandled_errors_total")

apps/blockchain-node/src/aitbc_chain/rpc/router.py

@@ -1849,21 +1849,16 @@ async def join_island(request: JoinIslandRequest) -> JoinIslandResponse:
 
 
 @router.post("/islands/leave", summary="Leave an island")
-@rate_limit(rate=100, per=60)
 async def leave_island(request: LeaveIslandRequest) -> LeaveIslandResponse:
     """
     Leave an island.
     Calls IslandManager.leave_island to remove the node from the specified island.
     """
     island_manager = get_island_manager()
-    logger.info(f'leave_island: island_manager={island_manager}')
     if island_manager is None:
-        logger.error('leave_island: island_manager is None!')
         raise HTTPException(status_code=503, detail="Island manager not available")
     
-    logger.info(f'leave_island: calling leave_island for {request.island_id}')
     success = island_manager.leave_island(request.island_id)
-    logger.info(f'leave_island: result={success}')
     
     if success:
         return LeaveIslandResponse(