Refactor ChecksumValidation as UploadInterceptor plugin

  - Convert from monkey-patching to clean plugin architecture
  - Break down monolithic upload handler into focused functions
  - Use onUploadComplete hook instead of direct status observers
  - Move ChecksumValidation.js to plugin folder structure
  - Remove direct UploaderModel prototype manipulation
  - Maintain all existing checksum generation and validation functionality

Author: Sunday-Crunk

src/js/core/ChecksumValidation.js

@@ -66,6 +66,8 @@ class UploadInterceptor {
       return;
     }
 
+    this.isPatched = true; // Set immediately to prevent double calls
+
     // Wait for UploaderModel to be available
     this.waitForUploaderModel().then(() => {
       this.applyUploadPatch();
@@ -92,7 +94,6 @@ class UploadInterceptor {
     // Override the uploadPresigned method
     UploaderModel.UploadItem.prototype.uploadPresigned = this.createPatchedUploadMethod();
 
-    this.isPatched = true;
     console.log('UploadInterceptor: Successfully patched upload system');
   }
 

src/js/core/UploadInterceptor/UploadInterceptor.js

@@ -6,17 +6,17 @@
  */
 
 import UploadInterceptor from './UploadInterceptor.js';
+import ChecksumValidationPlugin from './plugins/ChecksumValidation/ChecksumValidation.js';
 import UploadVolumeChecker from './plugins/UploadVolumeChecker/UploadVolumeChecker.js';
 
 // Initialize the upload interceptor system when DOM loads
 window.addEventListener("load", () => {
   console.log('UploadInterceptor: Initializing upload interception system');
 
   // Register plugins
+  UploadInterceptor.register(ChecksumValidationPlugin);
   UploadInterceptor.register(UploadVolumeChecker);
 
-  // Note: ChecksumValidation plugin will be registered here after refactoring
-
   console.log('UploadInterceptor: System initialized with plugins:', UploadInterceptor.getRegisteredPlugins());
 });