feat(feedback): Add content improvement feedback system

Frontend (frontend/app.js):

- Add textarea for improvement feedback

- Add submit button with loading state

- Handle API response and display improved content

Backend (backend/copywriter.py):

- Add improve_copy() method using Cohere API

- Integrate retry mechanism for API calls

Backend (backend/main.py):

- Add /improve-content POST endpoint

- Implement error handling and return improved content with metadata

Testing:

- Verified feedback submission flow

- Confirmed improved content generation

- Tested error scenarios and loading states

backend/models.py

@@ -0,0 +1,23 @@
+from datetime import datetime
+from sqlalchemy import Column, Integer, String, JSON, DateTime, Boolean, MetaData, Table, create_engine
+from databases import Database
+from config import DATA_DIR
+
+DATABASE_URL = f"sqlite:///{DATA_DIR}/training_data.db"
+database = Database(DATABASE_URL)
+metadata = MetaData()
+
+training_data = Table(
+    "training_data",
+    metadata,
+    Column("id", Integer, primary_key=True),
+    Column("content", String, nullable=False),
+    Column("content_type", String, nullable=False),
+    Column("metadata", JSON, nullable=False),
+    Column("added_at", DateTime, nullable=False, default=datetime.utcnow),
+    Column("is_training_data", Boolean, nullable=False, default=True)
+)
+
+# Create tables
+engine = create_engine(DATABASE_URL)
+metadata.create_all(engine)