fix(security): keep form drafts per user and delete them on logout

Drafts were stored in localStorage by form only, so on a shared phone
the next person was offered the previous user's unfinished entry
(colony observations, treatment and supplier details). Drafts are now
keyed by the signed-in user id and every draft is removed on logout,
like the offline cache already was.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Frontend/src/lib/auth/auth-context.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { createContext, useCallback, useContext, useEffect, useState, ReactNode } from 'react';
+import { clearAllFormDrafts } from '@/lib/forms/draft-storage';
 import {
   getCurrentUserRequest,
   isMfaRequired,
@@ -91,6 +92,8 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     await logoutRequest();
     storeAccessToken(null);
     setUser(null);
+    // Unfinished form entries belong to the person who typed them.
+    clearAllFormDrafts();
     // The service worker cache now holds real business data (colonies,
     // tasks, etc.) for offline viewing - on a shared/handed-off device
     // that must not survive into the next person's session.
@@ -134,6 +137,11 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   );
 }
 
+/** The signed-in user's id, or null - usable outside an AuthProvider (tests). */
+export function useCurrentUserId(): string | null {
+  return useContext(AuthContext)?.user?.id ?? null;
+}
+
 export function useAuth(): AuthContextValue {
   const context = useContext(AuthContext);
   if (!context) {

ApiCore-Frontend/src/lib/forms/draft-storage.spec.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it } from "vitest";
+import { renderHook } from "@testing-library/react";
+import { DRAFT_PREFIX, clearAllFormDrafts } from "./draft-storage";
+import { useFormDraft } from "./use-form-draft";
+
+describe("form drafts", () => {
+  it("removes every draft on logout and nothing else", () => {
+    window.localStorage.setItem(`${DRAFT_PREFIX}user-1:inspection-new`, "{}");
+    window.localStorage.setItem("apicore:motion", "subtle");
+
+    clearAllFormDrafts();
+
+    expect(window.localStorage.getItem(`${DRAFT_PREFIX}user-1:inspection-new`)).toBeNull();
+    expect(window.localStorage.getItem("apicore:motion")).toBe("subtle");
+  });
+
+  it("does not offer another user's draft", () => {
+    window.localStorage.setItem(
+      `${DRAFT_PREFIX}someone-else:inspection-new`,
+      JSON.stringify({ savedAt: Date.now(), values: { notes: "fremd" } }),
+    );
+
+    const { result } = renderHook(() => useFormDraft("inspection-new", {}, false));
+
+    expect(result.current.pending).toBeNull();
+  });
+});

ApiCore-Frontend/src/lib/forms/draft-storage.ts

@@ -0,0 +1,18 @@
+export const DRAFT_PREFIX = "apicore:draft:";
+
+/**
+ * Removes every draft on this device - called on logout, so the next
+ * person on a shared phone never sees someone else's unfinished entry.
+ */
+export function clearAllFormDrafts(): void {
+  try {
+    for (let index = window.localStorage.length - 1; index >= 0; index--) {
+      const storageKey = window.localStorage.key(index);
+      if (storageKey?.startsWith(DRAFT_PREFIX)) {
+        window.localStorage.removeItem(storageKey);
+      }
+    }
+  } catch {
+    // Storage unavailable - nothing stored either.
+  }
+}

ApiCore-Frontend/src/lib/forms/use-form-draft.ts

@@ -1,8 +1,9 @@
 "use client";
 
 import { useCallback, useEffect, useRef, useState } from "react";
+import { useCurrentUserId } from "@/lib/auth/auth-context";
 
-const PREFIX = "apicore:draft:";
+import { DRAFT_PREFIX as PREFIX } from "./draft-storage";
 const SAVE_DELAY_MS = 600;
 // Drafts older than this are stale (the situation at the hive has changed).
 const MAX_AGE_MS = 3 * 24 * 60 * 60 * 1000;
@@ -49,13 +50,18 @@ function remove(key: string): void {
  * sting, a dead battery) does not cost the typed-in entry. Saves only once
  * something was changed (`dirty`), never sends anything anywhere.
  */
-export function useFormDraft<T>(key: string, values: T, dirty: boolean): FormDraft<T> {
+export function useFormDraft<T>(formKey: string, values: T, dirty: boolean): FormDraft<T> {
+  // Drafts are per signed-in user: on a shared device nobody is offered
+  // someone else's entry.
+  const userId = useCurrentUserId();
+  const key = `${userId ?? "anonymous"}:${formKey}`;
   const [pending, setPending] = useState<FormDraft<T>["pending"]>(null);
-  const offered = useRef(false);
+  // Re-checked when the key changes (e.g. once the signed-in user is known).
+  const offeredKey = useRef<string | null>(null);
 
   useEffect(() => {
-    if (offered.current) return;
-    offered.current = true;
+    if (offeredKey.current === key) return;
+    offeredKey.current = key;
     const stored = read<T>(key);
     if (stored) {
       // Read after mount: localStorage does not exist during server render.