feat: Event archive management — Event model, migration, API, frontend page (Phase 8)

- Event ORM model with status/level enums, domain categories, review tracking
- Alembic migration e7f3a9b1c5d0 for events table
- Event crawler service with placeholder data (12 sample events)
- GET /api/v1/events with status/domain/search filtering and overdue_days
- EventArchivePage with filter toolbar (status, domain, search) and adaptive card grid
- Status badges, level badges, domain tags, overdue markers on event cards
- Loading/error/empty states, hover-to-honey card interaction

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

backend/app/models/event.py

@@ -0,0 +1,53 @@
+"""事件档案 ORM 模型。"""
+import uuid
+from datetime import datetime, date
+from sqlalchemy import String, DateTime, Date, Integer, Enum as SAEnum
+from sqlalchemy.orm import Mapped, mapped_column
+import enum
+
+from app.database import Base
+
+
+class EventStatus(str, enum.Enum):
+    ACTIVE = "active"
+    FADING = "fading"
+    DISSIPATING = "dissipating"
+    CLOSED = "closed"
+
+
+class EventLevel(str, enum.Enum):
+    A = "A"
+    B = "B"
+    C = "C"
+
+
+DOMAINS = [
+    "gateway",
+    "crawler",
+    "reporter",
+    "feishu",
+    "database",
+    "security",
+    "network",
+    "storage",
+    "monitor",
+    "scheduler",
+    "api",
+    "other",
+]
+
+
+class Event(Base):
+    __tablename__ = "events"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    level: Mapped[EventLevel] = mapped_column(SAEnum(EventLevel), nullable=False)
+    domain: Mapped[str] = mapped_column(String(50), nullable=False, index=True)
+    status: Mapped[EventStatus] = mapped_column(SAEnum(EventStatus), default=EventStatus.ACTIVE, nullable=False, index=True)
+    occurred_date: Mapped[date] = mapped_column(Date, nullable=False)
+    last_reviewed: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    no_new_info_count: Mapped[int] = mapped_column(Integer, default=0)
+    next_review: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+    updated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)