Implement complete user authentication system

- Configured Flask-Login with user_loader
- Added register, login, logout routes with proper validation
- Created login.html and register.html templates with auth forms
- Updated base.html navigation to show username and conditional menu
- Added auth page styling to style.css
- Protected all routes with @login_required decorator
- Updated all routes to filter by current_user.id
- Added user ownership validation for:
  - Channels (can only view/refresh own channels)
  - Videos (can only watch/download own videos)
  - Streams (can only stream videos from own channels)
- Updated save_to_db() calls to pass current_user.id
- Improved user_loader to properly handle session management

Features:
- User registration with password confirmation
- Secure password hashing with bcrypt
- Login with "remember me" functionality
- Flash messages for all auth actions
- Redirect to requested page after login
- User-specific data isolation (multi-tenant)

Security:
- All sensitive routes require authentication
- Users can only access their own data
- Passwords hashed with bcrypt salt
- Session-based authentication via Flask-Login

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

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

alembic/versions/c47f20eb915d_initial_schema_with_user_authentication.py

@@ -0,0 +1,95 @@
+"""Initial schema with user authentication
+
+Revision ID: c47f20eb915d
+Revises: 
+Create Date: 2025-11-26 14:25:12.933911
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'c47f20eb915d'
+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('users',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('username', sa.String(length=80), nullable=False),
+    sa.Column('email', sa.String(length=120), nullable=False),
+    sa.Column('password_hash', sa.String(length=255), nullable=False),
+    sa.Column('created_at', sa.DateTime(), nullable=False),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_users_email'), 'users', ['email'], unique=True)
+    op.create_index(op.f('ix_users_username'), 'users', ['username'], unique=True)
+    op.create_table('channels',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('user_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('rss_url', sa.String(length=500), nullable=False),
+    sa.Column('last_fetched_at', sa.DateTime(), nullable=True),
+    sa.ForeignKeyConstraint(['user_id'], ['users.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index('idx_user_channel', 'channels', ['user_id', 'channel_id'], unique=True)
+    op.create_index(op.f('ix_channels_channel_id'), 'channels', ['channel_id'], unique=False)
+    op.create_index(op.f('ix_channels_user_id'), 'channels', ['user_id'], unique=False)
+    op.create_table('video_entries',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('channel_id', sa.Integer(), nullable=False),
+    sa.Column('video_id', sa.String(length=50), nullable=False),
+    sa.Column('title', sa.String(length=500), nullable=False),
+    sa.Column('video_url', sa.String(length=500), nullable=False),
+    sa.Column('thumbnail_url', sa.String(length=500), nullable=True),
+    sa.Column('description', sa.Text(), nullable=True),
+    sa.Column('published_at', sa.DateTime(), nullable=False),
+    sa.Column('created_at', sa.DateTime(), nullable=False),
+    sa.Column('download_status', sa.Enum('PENDING', 'DOWNLOADING', 'COMPLETED', 'FAILED', name='downloadstatus'), nullable=False),
+    sa.Column('download_path', sa.String(length=1000), nullable=True),
+    sa.Column('download_started_at', sa.DateTime(), nullable=True),
+    sa.Column('download_completed_at', sa.DateTime(), nullable=True),
+    sa.Column('download_error', sa.String(length=2000), nullable=True),
+    sa.Column('file_size', sa.BigInteger(), nullable=True),
+    sa.ForeignKeyConstraint(['channel_id'], ['channels.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index('idx_channel_created', 'video_entries', ['channel_id', 'created_at'], unique=False)
+    op.create_index('idx_download_status', 'video_entries', ['download_status'], unique=False)
+    op.create_index('idx_published_at', 'video_entries', ['published_at'], unique=False)
+    op.create_index('idx_video_id_channel', 'video_entries', ['video_id', 'channel_id'], unique=True)
+    op.create_index(op.f('ix_video_entries_published_at'), 'video_entries', ['published_at'], unique=False)
+    op.create_index(op.f('ix_video_entries_video_id'), 'video_entries', ['video_id'], unique=False)
+    op.create_index(op.f('ix_video_entries_video_url'), 'video_entries', ['video_url'], unique=False)
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.drop_index(op.f('ix_video_entries_video_url'), table_name='video_entries')
+    op.drop_index(op.f('ix_video_entries_video_id'), table_name='video_entries')
+    op.drop_index(op.f('ix_video_entries_published_at'), table_name='video_entries')
+    op.drop_index('idx_video_id_channel', table_name='video_entries')
+    op.drop_index('idx_published_at', table_name='video_entries')
+    op.drop_index('idx_download_status', table_name='video_entries')
+    op.drop_index('idx_channel_created', table_name='video_entries')
+    op.drop_table('video_entries')
+    op.drop_index(op.f('ix_channels_user_id'), table_name='channels')
+    op.drop_index(op.f('ix_channels_channel_id'), table_name='channels')
+    op.drop_index('idx_user_channel', table_name='channels')
+    op.drop_table('channels')
+    op.drop_index(op.f('ix_users_username'), table_name='users')
+    op.drop_index(op.f('ix_users_email'), table_name='users')
+    op.drop_table('users')
+    # ### end Alembic commands ###