Add SQLAlchemy ORM with Alembic migrations

- Added SQLAlchemy 2.0 and Alembic 1.13 dependencies
- Created models.py with Channel and VideoEntry ORM models
- Created database.py for database configuration and session management
- Initialized Alembic migration system with initial migration
- Updated feed_parser.py with save_to_db() method for persistence
- Updated main.py with database initialization and new API routes:
  - /api/feed now saves to database by default
  - /api/channels lists all tracked channels
  - /api/history/<channel_id> returns video history
- Updated .gitignore to exclude database files
- Updated CLAUDE.md with comprehensive ORM and migration documentation

Database uses SQLite (yottob.db) with upsert logic to avoid duplicates.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

alembic/README

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+Generic single-database configuration.

alembic/env.py

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+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+from models import Base
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, Sequence[str], None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}

alembic/versions/270efe6976bc_initial_migration_channel_and_.py

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+"""Initial migration: Channel and VideoEntry tables
+
+Revision ID: 270efe6976bc
+Revises: 
+Create Date: 2025-11-26 13:55:52.270543
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '270efe6976bc'
+down_revision: Union[str, Sequence[str], None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.create_table('channels',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('channel_id', sa.String(length=50), nullable=False),
+    sa.Column('title', sa.String(length=200), nullable=False),
+    sa.Column('link', sa.String(length=500), nullable=False),
+    sa.Column('last_fetched', sa.DateTime(), nullable=False),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_channels_channel_id'), 'channels', ['channel_id'], unique=True)
+    op.create_table('video_entries',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('channel_id', sa.Integer(), nullable=False),
+    sa.Column('title', sa.String(length=500), nullable=False),
+    sa.Column('link', sa.String(length=500), nullable=False),
+    sa.Column('created_at', sa.DateTime(), nullable=False),
+    sa.ForeignKeyConstraint(['channel_id'], ['channels.id'], ),
+    sa.PrimaryKeyConstraint('id'),
+    sa.UniqueConstraint('link')
+    )
+    op.create_index('idx_channel_created', 'video_entries', ['channel_id', 'created_at'], unique=False)
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index('idx_channel_created', table_name='video_entries')
+    op.drop_table('video_entries')
+    op.drop_index(op.f('ix_channels_channel_id'), table_name='channels')
+    op.drop_table('channels')
+    # ### end Alembic commands ###