Implement full system directory browser modal for temp directories

- Add GET /api/system/browse-dir and POST /api/system/create-dir endpoints
- Add Folder Browser Modal overlay in index.html
- Add browse buttons to both job-specific and default setting temp dir inputs
- Add JS helpers and event handlers for directory list loading, parent navigation, directory selection, and new folder creation

app/main.py

@@ -1113,6 +1113,65 @@ def update_settings(req: UpdateSettingsRequest):
     save_settings(settings)
     return {"status": "saved", "settings": settings}
 
+
+class CreateDirRequest(BaseModel):
+    parent_path: str
+    name: str
+
+@app.get("/api/system/browse-dir")
+def browse_dir(path: str = ""):
+    """Browse directories on the system"""
+    if not path:
+        path = os.path.expanduser("~")
+    
+    path = os.path.abspath(path)
+    
+    if not os.path.exists(path):
+        raise HTTPException(status_code=404, detail="Path does not exist")
+        
+    if not os.path.isdir(path):
+        raise HTTPException(status_code=400, detail="Path is not a directory")
+        
+    try:
+        entries = []
+        # Add parent directory entry if not at root
+        parent = os.path.dirname(path)
+        if parent != path:
+            entries.append({
+                "name": "..",
+                "path": parent,
+                "is_dir": True
+            })
+            
+        for name in sorted(os.listdir(path)):
+            full_path = os.path.join(path, name)
+            try:
+                if os.path.isdir(full_path):
+                    entries.append({
+                        "name": name,
+                        "path": full_path,
+                        "is_dir": True
+                    })
+            except PermissionError:
+                continue
+                
+        return {
+            "current_path": path,
+            "entries": entries
+        }
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+@app.post("/api/system/create-dir")
+def create_dir(req: CreateDirRequest):
+    """Create a new directory"""
+    full_path = os.path.abspath(os.path.join(req.parent_path, req.name))
+    try:
+        os.makedirs(full_path, exist_ok=True)
+        return {"status": "ok", "path": full_path}
+    except Exception as e:
+        raise HTTPException(status_code=400, detail=str(e))
+
 @app.get("/api/uploads/{filename}")
 def get_upload_file(filename: str):
     file_path = os.path.join(upscaler.UPLOAD_DIR, filename)