fix: set account_id on all Session constructors; fix 3 ESLint errors in CI

Backend: start_session, prepare_session, batch_launch_sessions all missing
account_id=current_user.account_id — Phase 1 NOT NULL constraint made these
500 in test suite (test_ratings.py fixture couldn't create sessions).

Frontend ESLint:
- TaskLane.tsx: suppress react-refresh/only-export-components for clearTaskState
- TeamSummary.tsx: init loading from isAccountOwner to avoid sync setState in effect
- ScriptBodyEditor.tsx: move lastValueRef.current assignment into useEffect

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

frontend/src/components/script-editor/ScriptBodyEditor.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useRef } from 'react'
+import { useCallback, useEffect, useRef } from 'react'
 import Editor, { type BeforeMount } from '@monaco-editor/react'
 import { resolutionFlowTheme, THEME_ID } from '@/components/tree-editor/code-mode/resolutionFlowTheme'
 import { Spinner } from '@/components/common/Spinner'
@@ -11,7 +11,9 @@ interface Props {
 
 export function ScriptBodyEditor({ value, onChange, disabled }: Props) {
   const lastValueRef = useRef(value)
-  lastValueRef.current = value
+  useEffect(() => {
+    lastValueRef.current = value
+  }, [value])
 
   const handleBeforeMount: BeforeMount = useCallback((monaco) => {
     // Register our dark theme if not already defined