feat: extract shared infrastructure from shared_lib

Phase 1-3 of decoupling plan:
- Shared DB, models, infrastructure, browser, config, utils
- Event infrastructure (domain_events outbox, bus, processor)
- Structured logging
- Generic container concept (container_type/container_id)
- Alembic migrations for all schema changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

alembic/versions/a9f54e4eaf02_add_menu_items_table.py

@@ -0,0 +1,37 @@
+
+# Alembic migration script template
+
+"""add menu_items table
+
+Revision ID: a9f54e4eaf02
+Revises: 6cb124491c9d
+Create Date: 2025-12-07 17:38:54.839296
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = 'a9f54e4eaf02'
+down_revision = '6cb124491c9d'
+branch_labels = None
+depends_on = None
+
+def upgrade() -> None:
+    op.create_table('menu_items',
+        sa.Column('id', sa.Integer(), autoincrement=True, nullable=False),
+        sa.Column('post_id', sa.Integer(), nullable=False),
+        sa.Column('sort_order', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(timezone=True), server_default=sa.text('now()'), nullable=False),
+        sa.Column('updated_at', sa.DateTime(timezone=True), server_default=sa.text('now()'), nullable=False),
+        sa.Column('deleted_at', sa.DateTime(timezone=True), nullable=True),
+        sa.ForeignKeyConstraint(['post_id'], ['posts.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_menu_items_post_id'), 'menu_items', ['post_id'], unique=False)
+    op.create_index(op.f('ix_menu_items_sort_order'), 'menu_items', ['sort_order'], unique=False)
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_menu_items_sort_order'), table_name='menu_items')
+    op.drop_index(op.f('ix_menu_items_post_id'), table_name='menu_items')
+    op.drop_table('menu_items')