feat: implement update_memory tool and routes for user memory management

surfsense_backend/app/routes/memory_routes.py

@@ -0,0 +1,46 @@
+"""Routes for user memory management (personal memory.md)."""
+
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.agents.new_chat.tools.update_memory import MEMORY_HARD_LIMIT
+from app.db import User, get_async_session
+from app.users import current_active_user
+
+router = APIRouter()
+
+
+class MemoryRead(BaseModel):
+    memory_md: str
+
+
+class MemoryUpdate(BaseModel):
+    memory_md: str
+
+
+@router.get("/users/me/memory", response_model=MemoryRead)
+async def get_user_memory(
+    user: User = Depends(current_active_user),
+    session: AsyncSession = Depends(get_async_session),
+):
+    await session.refresh(user, ["memory_md"])
+    return MemoryRead(memory_md=user.memory_md or "")
+
+
+@router.put("/users/me/memory", response_model=MemoryRead)
+async def update_user_memory(
+    body: MemoryUpdate,
+    user: User = Depends(current_active_user),
+    session: AsyncSession = Depends(get_async_session),
+):
+    if len(body.memory_md) > MEMORY_HARD_LIMIT:
+        raise HTTPException(
+            status_code=400,
+            detail=f"Memory exceeds {MEMORY_HARD_LIMIT:,} character limit ({len(body.memory_md):,} chars).",
+        )
+    user.memory_md = body.memory_md
+    session.add(user)
+    await session.commit()
+    await session.refresh(user, ["memory_md"])
+    return MemoryRead(memory_md=user.memory_md or "")