Fix/desktop open with tool access (Stirling-Tools#6056)

## Description

Fixes Stirling-Tools#6029 - Additional selection in windows client no longer necessary

## Problem
When opening PDF files in the Windows desktop client using "Open with",
the file displays properly but users had to manually select it again in
the workbench before any PDF tools (merge, compress, crop, compare,
etc.) become functional.

## Root Cause
Files opened via "Open with" were added to FileContext but **not
selected** (missing `selectFiles: true`). Without selection, the file
wasn't marked as active, preventing tool access.

Additionally, `AppInitializer` was placed outside
`ToolWorkflowProvider`, causing a context error.

## Solution

### Changes:
1. **frontend/src/desktop/hooks/useAppInitialization.ts**
   - Added `{ selectFiles: true }` when calling `addFiles()`
   - Files now immediately marked as active in FileContext

2. **frontend/src/core/components/AppProviders.tsx**
   - Moved `AppInitializer` inside `ToolWorkflowProvider`
   - Ensures context availability for initialization

## Testing
- Open PDF via "Open with" on Windows
- File now immediately usable with all tools
- No manual reselection needed

## Screenshot
<img width="1920" height="1080" alt="Screenshot (3)"
src="https://github.com/user-attachments/assets/9ceacadf-eb12-42a6-86f9-bca6188bfbb9"
/>

---------

Co-authored-by: Anthony Stirling <77850077+Frooodle@users.noreply.github.com>
Co-authored-by: EthanHealy01 <80844253+EthanHealy01@users.noreply.github.com>
Co-authored-by: Reece Browne <74901996+reecebrowne@users.noreply.github.com>

Author: 4 people

frontend/src/desktop/hooks/useAppInitialization.ts

@@ -59,7 +59,7 @@ export function useAppInitialization(): void {
           const filesArray = loadedFiles.map(entry => entry.file);
           const quickKeyToPath = new Map(loadedFiles.map(entry => [entry.quickKey, entry.filePath]));
 
-          const addedFiles = await addFiles(filesArray);
+          const addedFiles = await addFiles(filesArray, { selectFiles: true });
           addedFiles.forEach(file => {
             const localFilePath = quickKeyToPath.get(file.quickKey);
             if (localFilePath) {