Refactor: Modularize lib_general.py by extracting core functionalities.

- Extracted Email functions to app/lib_email.py.
- Extracted Export functions to app/lib_export.py.
- Extracted JWT utilities to app/lib_jwt.py.
- Extracted Hash utilities to app/lib_hash.py.
- Updated app/lib_general.py to import from these new modules for backward compatibility.
- Updated V3 Frontend API Guide with latest security and site_domain exception details.

app/lib_jwt.py

@@ -0,0 +1,68 @@
+import jwt
+import time
+import logging
+from typing import Dict, Optional
+
+from app.log import logger_reset
+
+log = logging.getLogger(__name__)
+
+# ### BEGIN ### API Lib JWT ### sign_jwt() ###
+# Moved from lib_general.py 2026-01-07
+@logger_reset
+def sign_jwt(
+        secret_key: str, # Secret/Private/Password
+        ttl: int = 60, # Default to 60 seconds
+        max_renew: int = 0, # Default to 0
+        public_key: str = None, # Will be part of the token. Use to look up secret when verifying.???
+        account_id: str = None,
+        person_id: str = None,
+        user_id: str = None,
+        json_str: str = None,
+        b64_str: str = None,
+        ) -> str:
+    log.setLevel(logging.WARNING) # DEBUG, INFO, WARNING, ERROR, EXCEPTION, CRITICAL
+    log.debug(locals())
+
+    payload = {
+        'iat': time.time(), # Issued at
+        'eat': time.time() + ttl, # Expires at
+        'max_renew': max_renew, # Number of times allowed to request renew without API secret key
+        'public_key': public_key, # Use to lookup the secret/private/password key when verifying
+        'account_id': account_id,
+        'person_id': person_id,
+        'user_id': user_id,
+        'json_str': json_str,
+        'b64_str': b64_str,
+    }
+    secret = secret_key
+    algorithm = 'HS256'
+    token = jwt.encode(payload, secret, algorithm=algorithm)
+
+    log.debug(token)
+
+    return token
+# ### END ### API Lib JWT ### sign_jwt() ###
+
+
+# ### BEGIN ### API Lib JWT ### decode_jwt() ###
+# Moved from lib_general.py 2026-01-07
+@logger_reset
+def decode_jwt(
+        secret_key: str,
+        token: str,
+        ) -> Optional[dict]:
+    log.setLevel(logging.WARNING) # DEBUG, INFO, WARNING, ERROR, EXCEPTION, CRITICAL
+    log.debug(locals())
+
+    secret = secret_key
+    algorithm = 'HS256'
+
+    try:
+        decoded_token = jwt.decode(token, secret, algorithms=[algorithm])
+        log.debug(decoded_token)
+        if decoded_token['eat'] >= time.time(): return decoded_token
+        else: return False
+    except:
+        return None
+# ### END ### API Lib JWT ### decode_jwt() ###