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/env.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+import os, sys
+from logging.config import fileConfig
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+
+config = context.config
+
+if config.config_file_name is not None:
+    try:
+        fileConfig(config.config_file_name)
+    except Exception:
+        pass
+
+# Add project root so all app model packages are importable
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../..")))
+
+from shared.db.base import Base
+
+# Import ALL models so Base.metadata sees every table
+import shared.models  # noqa: F401  User, KV, MagicLink, MenuItem, Ghost*
+import blog.models  # noqa: F401  Post, Author, Tag, Snippet, TagGroup
+import market.models  # noqa: F401  Product, CartItem, MarketPlace, etc.
+import cart.models  # noqa: F401  Order, OrderItem, PageConfig
+import events.models  # noqa: F401  Calendar, CalendarEntry, Ticket, etc.
+
+target_metadata = Base.metadata
+
+def _get_url() -> str:
+    url = os.getenv(
+        "ALEMBIC_DATABASE_URL",
+        os.getenv("DATABASE_URL", config.get_main_option("sqlalchemy.url") or "")
+    )
+    print(url)
+    return url
+
+def run_migrations_offline() -> None:
+    url = _get_url()
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+        compare_type=True,
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+def run_migrations_online() -> None:
+    url = _get_url()
+    if url:
+        config.set_main_option("sqlalchemy.url", url)
+
+    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, compare_type=True)
+        with context.begin_transaction():
+            context.run_migrations()
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()