Fix session expiry: use config value, increase to 7 days

- LOGIN was ignoring ACCESS_TOKEN_EXPIRE_MINUTES (hardcoded 15min default)
- Pass expires_delta from config in login route
- Increase token lifetime from 30min to 7 days

dashboard/backend/routers/auth.py

@@ -1,3 +1,4 @@
+from datetime import timedelta
 from fastapi import APIRouter, Depends, HTTPException, status
 from pydantic import BaseModel
 import config
@@ -51,7 +52,10 @@ async def login(creds: LoginRequest):
                 headers={"WWW-Authenticate": "Bearer"},
             )
 
-    access_token = auth.create_access_token(data={"sub": creds.username})
+    access_token = auth.create_access_token(
+        data={"sub": creds.username},
+        expires_delta=timedelta(minutes=config.ACCESS_TOKEN_EXPIRE_MINUTES),
+    )
     return {
         "access_token": access_token, 
         "token_type": "bearer",