fix(annotations): fix error 300 on sign frontend (#5536)

# Description of Changes

the bug


https://github.com/user-attachments/assets/7f524c95-e57a-4188-a7a9-8d3020a3bb47


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## Checklist

### General

- [X] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [X] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [X] I have performed a self-review of my own code
- [X] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [X] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

Signed-off-by: Balázs Szücs <[email protected]>

frontend/src/core/components/shared/Tooltip.tsx

@@ -83,7 +83,10 @@ export const Tooltip: React.FC<TooltipProps> = ({
     }
   }, []);
 
-  const sidebarContext = sidebarTooltip ? useSidebarContext() : null;
+  // Always call the hook unconditionally to satisfy React's rules of hooks.
+  // The context is only used when sidebarTooltip is true.
+  const sidebarContextValue = useSidebarContext();
+  const sidebarContext = sidebarTooltip ? sidebarContextValue : null;
 
   const isControlled = controlledOpen !== undefined;
   const open = (isControlled ? !!controlledOpen : internalOpen) && !disabled;

frontend/src/core/components/shared/rightRail/ViewerAnnotationControls.tsx

@@ -55,11 +55,6 @@ export default function ViewerAnnotationControls({ currentView, disabled = false
   const isAnnotateActive = selectedTool === 'annotate';
   const annotationsHidden = viewerContext ? !viewerContext.isAnnotationsVisible : false;
 
-  // Don't show any annotation controls in sign mode
-  if (isSignMode) {
-    return null;
-  }
-
   // Persist annotations to file if there are unsaved changes
   const saveAnnotationsIfNeeded = async () => {
     if (!viewerContext?.exportActions?.saveAsCopy || currentView !== 'viewer' || !historyApiRef?.current?.canUndo()) return;
@@ -135,6 +130,11 @@ export default function ViewerAnnotationControls({ currentView, disabled = false
     }
   };
 
+  // Don't show any annotation controls in sign mode
+  // NOTE: This early return is placed AFTER all hooks to satisfy React's rules of hooks
+  if (isSignMode) {
+    return null;
+  }
 
   return (
     <>

frontend/src/core/contexts/FileContext.tsx

@@ -54,8 +54,10 @@ function FileContextInner({
 }: FileContextProviderProps) {
   const [state, dispatch] = useReducer(fileContextReducer, initialFileContextState);
 
-  // IndexedDB context for persistence
+  // Always call the hook unconditionally to satisfy React's rules of hooks.
-  const indexedDB = enablePersistence ? useIndexedDB() : null;
+  // IndexedDB context is only used when enablePersistence is true.
+  const indexedDBValue = useIndexedDB();
+  const indexedDB = enablePersistence ? indexedDBValue : null;
 
   // File ref map - stores File objects outside React state
   const filesRef = useRef<Map<FileId, File>>(new Map());