Add brain memory services and APIs

Introduce the backend pieces for brain memory ingestion, routing, and
system telemetry so the new knowledge workflows can project data into a
brain view. The supporting tests lock in the new behavior and keep the
expanded backend surface stable.

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

backend/app/routers/brain.py

@@ -0,0 +1,61 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.database import get_db
+from app.models.user import User
+from app.routers.auth import get_current_user
+from app.schemas.brain import (
+    BrainEventOut,
+    BrainLearnRunOut,
+    BrainMemoryOut,
+    BrainOverviewOut,
+    BrainTagGroupsOut,
+)
+from app.services.brain_service import BrainService
+
+router = APIRouter(prefix="/api/brain", tags=["知识大脑"])
+
+
+@router.get("/overview", response_model=BrainOverviewOut)
+async def get_brain_overview(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    service = BrainService(db)
+    return await service.get_overview(current_user.id)
+
+
+@router.get("/memories", response_model=list[BrainMemoryOut])
+async def list_brain_memories(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    service = BrainService(db)
+    return await service.list_memories(current_user.id)
+
+
+@router.get("/tags", response_model=BrainTagGroupsOut)
+async def list_brain_tags(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    service = BrainService(db)
+    return await service.list_tags(current_user.id)
+
+
+@router.get("/events", response_model=list[BrainEventOut])
+async def list_brain_events(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    service = BrainService(db)
+    return await service.list_events(current_user.id)
+
+
+@router.post("/learn/run", response_model=BrainLearnRunOut)
+async def run_brain_learning(
+    current_user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    service = BrainService(db)
+    return await service.run_learning(current_user.id)