feat: Complete modular plugin architecture v0.17.0

Major architectural refactor:
- Convert invcount and conssheets to self-contained modules
- Add Module Manager with upload/install/uninstall
- Implement auto-restart after module installation
- Add drag-and-drop module upload system
- Create triple-confirmation uninstall flow
- Redesign Module Manager UI with card layout
- Support dynamic module loading from /modules/

This enables easy distribution and installation of new modules
without code changes to core application.

app.py

@@ -28,7 +28,7 @@ app.config['PERMANENT_SESSION_LIFETIME'] = timedelta(hours=1)
 
 
 # 1. Define the version
-APP_VERSION = '0.16.0'  # Bumped version for modular architecture
+APP_VERSION = '0.17.0'  # Bumped version for modular architecture
 
 # 2. Inject it into all templates automatically
 @app.context_processor
@@ -236,6 +236,125 @@ def restart_server():
         
     except Exception as e:
         return jsonify({'success': False, 'message': f'Restart failed: {str(e)}'})
+    
+
+"""
+Add this route to app.py
+"""
+
+@app.route('/admin/modules/upload', methods=['POST'])
+@login_required
+def upload_module():
+    """Upload and extract a module package"""
+    if session.get('role') not in ['owner', 'admin']:
+        return jsonify({'success': False, 'message': 'Access denied'}), 403
+    
+    if 'module_file' not in request.files:
+        return jsonify({'success': False, 'message': 'No file uploaded'})
+    
+    file = request.files['module_file']
+    
+    if file.filename == '':
+        return jsonify({'success': False, 'message': 'No file selected'})
+    
+    if not file.filename.endswith('.zip'):
+        return jsonify({'success': False, 'message': 'File must be a ZIP archive'})
+    
+    try:
+        import zipfile
+        import tempfile
+        import shutil
+        from pathlib import Path
+        import json
+        
+        # Create temp directory
+        with tempfile.TemporaryDirectory() as temp_dir:
+            # Save uploaded file
+            zip_path = os.path.join(temp_dir, 'module.zip')
+            file.save(zip_path)
+            
+            # Extract zip
+            with zipfile.ZipFile(zip_path, 'r') as zip_ref:
+                zip_ref.extractall(temp_dir)
+            
+            # Find the module folder (should contain manifest.json)
+            module_folder = None
+            manifest_path = None
+            
+            # Check if manifest.json is at root of zip
+            if os.path.exists(os.path.join(temp_dir, 'manifest.json')):
+                module_folder = temp_dir
+                manifest_path = os.path.join(temp_dir, 'manifest.json')
+            else:
+                # Look for manifest.json in subdirectories
+                for item in os.listdir(temp_dir):
+                    item_path = os.path.join(temp_dir, item)
+                    if os.path.isdir(item_path):
+                        potential_manifest = os.path.join(item_path, 'manifest.json')
+                        if os.path.exists(potential_manifest):
+                            module_folder = item_path
+                            manifest_path = potential_manifest
+                            break
+            
+            if not manifest_path:
+                return jsonify({
+                    'success': False, 
+                    'message': 'Invalid module package: manifest.json not found'
+                })
+            
+            # Read and validate manifest
+            with open(manifest_path, 'r') as f:
+                manifest = json.load(f)
+            
+            required_fields = ['module_key', 'name', 'version', 'author']
+            for field in required_fields:
+                if field not in manifest:
+                    return jsonify({
+                        'success': False,
+                        'message': f'Invalid manifest.json: missing required field "{field}"'
+                    })
+            
+            module_key = manifest['module_key']
+            
+            # Check if module already exists
+            modules_dir = os.path.join(os.path.dirname(__file__), 'modules')
+            target_path = os.path.join(modules_dir, module_key)
+            
+            if os.path.exists(target_path):
+                return jsonify({
+                    'success': False,
+                    'message': f'Module "{module_key}" already exists. Please uninstall it first or use a different module key.'
+                })
+            
+            # Required files check
+            required_files = ['manifest.json', '__init__.py']
+            for req_file in required_files:
+                if not os.path.exists(os.path.join(module_folder, req_file)):
+                    return jsonify({
+                        'success': False,
+                        'message': f'Invalid module package: {req_file} not found'
+                    })
+            
+            # Copy module to /modules directory
+            shutil.copytree(module_folder, target_path)
+            
+            print(f"✅ Module '{manifest['name']}' uploaded successfully to {target_path}")
+            
+            return jsonify({
+                'success': True,
+                'message': f"Module '{manifest['name']}' uploaded successfully! Click Install to activate it."
+            })
+            
+    except zipfile.BadZipFile:
+        return jsonify({'success': False, 'message': 'Invalid ZIP file'})
+    except json.JSONDecodeError:
+        return jsonify({'success': False, 'message': 'Invalid manifest.json: not valid JSON'})
+    except Exception as e:
+        print(f"❌ Module upload error: {e}")
+        import traceback
+        traceback.print_exc()
+        return jsonify({'success': False, 'message': f'Upload failed: {str(e)}'})
+
 # ==================== PWA SUPPORT ROUTES ====================
 
 @app.route('/manifest.json')