Fix CancelledError handling in connection pool to prevent connection leaks

Problem: High-concurrency streaming requests with client disconnects trigger
asyncio.CancelledError (BaseException in Python 3.8+), but exception handlers
only caught Exception, causing:
- yielded_sqlor.used permanently stays True
- sqlor.exit() never called
- Connection slots permanently consumed, eventual pool exhaustion

Fix:
1. SqlorPool.context(): Use try/finally instead of try/except to always
   reset yielded_sqlor.used=False, even on CancelledError
2. DBPools.sqlorContext(): Change except Exception to except BaseException,
   add finally block to always call sqlor.exit(), suppress CancelledError
   logging noise

Verification: Ad-hoc tests confirm connections properly reset on cancellation
and can be reused. Normal exceptions still propagate correctly.

sqlor/dbpools.py

@@ -126,13 +126,10 @@ class SqlorPool:
 			yielded_sqlor.use_at = time.time()
 			try:
 				yield yielded_sqlor.sqlor
+			finally:
+				# Always reset state, even on CancelledError (BaseException in Python 3.8+)
 				yielded_sqlor.used = False
 				yielded_sqlor.use_at = time.time()
-				return
-			except Exception as e:
-				yielded_sqlor.used = False
-				yielded_sqlor.use_at = time.time()
-				raise e
 			
 
 @SingletonDecorator
@@ -178,17 +175,23 @@ class DBPools(EventDispatcher):
 				yield sqlor
 				if sqlor and sqlor.dataChanged:
 					await sqlor.commit()
-				await sqlor.exit()
-			except Exception as e:
+			except BaseException as e:
 				self.e_except = e
-				cb = format_exc()
-				exception(f'sqlorContext():EXCEPTION{e}, {cb}')
+				if not isinstance(e, asyncio.CancelledError):
+					cb = format_exc()
+					exception(f'sqlorContext():EXCEPTION{e}, {cb}')
 				try:
 					await sqlor.rollback()
 				except:
 					pass
-				await sqlor.exit()
-				raise e
+				raise
+			finally:
+				# Always call exit(), even on CancelledError (BaseException in Python 3.8+)
+				if sqlor:
+					try:
+						await sqlor.exit()
+					except:
+						pass
 	
 	def get_exception(self):
 		return self.e_except