refactor: replace requests with httpx in Bitcoin wallet and blockchain services

- Replace requests.Session with httpx.Client in BitcoinWallet class
- Add graceful fallback when httpx is not available with HTTP_CLIENT_AVAILABLE flag
- Add session null check in _rpc_call to prevent errors when httpx unavailable
- Update get_balance in blockchain service to use httpx.Client context manager
- Add warning log when httpx import fails to disable wallet functions

apps/coordinator-api/src/app/services/bitcoin_wallet.py

@@ -7,9 +7,15 @@ Uses RPC to connect to Bitcoin Core (or alternative like Block.io)
 import os
 import json
 import logging
-import requests
 from typing import Dict, Optional
 
+try:
+    import httpx
+    HTTP_CLIENT_AVAILABLE = True
+except ImportError:
+    HTTP_CLIENT_AVAILABLE = False
+    logging.warning("httpx not available, bitcoin wallet functions will be disabled")
+
 logger = logging.getLogger(__name__)
 
 # Bitcoin wallet configuration (credentials from environment)
@@ -25,8 +31,12 @@ WALLET_CONFIG = {
 class BitcoinWallet:
     def __init__(self):
         self.config = WALLET_CONFIG
-        self.session = requests.Session()
-        self.session.auth = (self.config['rpc_user'], self.config['rpc_password'])
+        if not HTTP_CLIENT_AVAILABLE:
+            logger.error("httpx not available - bitcoin wallet functions disabled")
+            self.session = None
+        else:
+            self.session = httpx.Client()
+            self.session.auth = (self.config['rpc_user'], self.config['rpc_password'])
         
     def get_balance(self) -> float:
         """Get the current Bitcoin balance"""
@@ -68,6 +78,9 @@ class BitcoinWallet:
         """Make an RPC call to Bitcoin Core"""
         if params is None:
             params = []
+        
+        if not self.session:
+            return {"error": "httpx not available"}
             
         payload = {
             "jsonrpc": "2.0",

apps/coordinator-api/src/app/services/blockchain.py

@@ -35,16 +35,15 @@ def get_balance(address: str) -> Optional[float]:
     """Get AITBC balance for an address"""
     
     try:
-        import requests
-        
-        response = requests.get(
-            f"{BLOCKCHAIN_RPC}/getBalance/{address}",
-            headers={"X-Api-Key": settings.admin_api_keys[0] if settings.admin_api_keys else ""}
-        )
-        
-        if response.status_code == 200:
-            data = response.json()
-            return float(data.get("balance", 0))
+        with httpx.Client() as client:
+            response = client.get(
+                f"{BLOCKCHAIN_RPC}/getBalance/{address}",
+                headers={"X-Api-Key": settings.admin_api_keys[0] if settings.admin_api_keys else ""}
+            )
+            
+            if response.status_code == 200:
+                data = response.json()
+                return float(data.get("balance", 0))
         
     except Exception as e:
         logger.error("Error getting balance: %s", e)