feat(auth): add session-based login/logout with bcrypt hashing, seed default admin, templates and navbar updates; add auth middleware; pin SQLAlchemy 1.4.x for Py3.13; update TODOs

app/models.py

@@ -6,8 +6,11 @@ All models inherit from Base which is configured in the database module.
 
 from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Float, Text, Boolean
 from sqlalchemy.orm import relationship
+from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.sql import func
-from .database import Base
+
+# Create Base for SQLAlchemy 1.x compatibility
+Base = declarative_base()
 
 
 class User(Base):