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>

models/domain_event.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+from datetime import datetime
+from sqlalchemy import String, Integer, DateTime, Text, func
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import Mapped, mapped_column
+from shared.db.base import Base
+
+
+class DomainEvent(Base):
+    __tablename__ = "domain_events"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    event_type: Mapped[str] = mapped_column(String(128), nullable=False, index=True)
+    aggregate_type: Mapped[str] = mapped_column(String(64), nullable=False)
+    aggregate_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    payload: Mapped[dict | None] = mapped_column(JSONB, nullable=True)
+    state: Mapped[str] = mapped_column(
+        String(20), nullable=False, default="pending", server_default="pending", index=True
+    )
+    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    max_attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=5, server_default="5")
+    last_error: Mapped[str | None] = mapped_column(Text, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
+    processed_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
+
+    def __repr__(self) -> str:
+        return f"<DomainEvent {self.id} {self.event_type} [{self.state}]>"