refactor: companion FrameServer and related (substantive only, no Black)

Reapply refactor from ce8381a (replace monolithic FrameServer with thin
pymc_core subclass, re-export constants, SQLite persistence hooks) while
preserving pre-refactor whitespace where patch applied cleanly. Remaining
files match refactor commit exactly. Diff vs ce8381a is whitespace-only.

Co-authored-by: Cursor <cursoragent@cursor.com>

repeater/web/auth/jwt_handler.py

@@ -1,10 +1,12 @@
-import jwt
+import logging
 import time
 from typing import Dict, Optional
-import logging
+
+import jwt
 
 logger = logging.getLogger(__name__)
 
+
 class JWTHandler:
     def __init__(self, secret: str, expiry_minutes: int = 15):
         self.secret = secret
@@ -14,21 +16,16 @@ class JWTHandler:
 
         now = int(time.time())
         expiry = now + (self.expiry_minutes * 60)
-        
-        payload = {
-            'sub': username,
-            'exp': expiry,
-            'iat': now,
-            'client_id': client_id
-        }
-        
-        token = jwt.encode(payload, self.secret, algorithm='HS256')
+
+        payload = {"sub": username, "exp": expiry, "iat": now, "client_id": client_id}
+
+        token = jwt.encode(payload, self.secret, algorithm="HS256")
         logger.info(f"Created JWT for user '{username}' with client_id '{client_id[:8]}...'")
         return token
-    
+
     def verify_jwt(self, token: str) -> Optional[Dict]:
         try:
-            payload = jwt.decode(token, self.secret, algorithms=['HS256'])
+            payload = jwt.decode(token, self.secret, algorithms=["HS256"])
             return payload
         except jwt.ExpiredSignatureError:
             logger.warning("JWT token expired")