feat: Implement modular plugin architecture

- Convert invcount to self-contained module
- Add Module Manager for install/uninstall
- Create module_registry database table
- Support hot-reloading of modules
- Move data imports into invcount module
- Update all templates and routes to new structure

Version bumped to 0.16.0

modules/invcount/__init__.py

@@ -0,0 +1,20 @@
+"""
+Inventory Counts Module
+Handles cycle counting and physical inventory workflows
+"""
+from flask import Blueprint
+
+def create_blueprint():
+    """Create and return the invcount blueprint"""
+    bp = Blueprint(
+        'invcount',
+        __name__,
+        template_folder='templates',
+        url_prefix='/invcount'
+    )
+    
+    # Import and register routes
+    from .routes import register_routes
+    register_routes(bp)
+    
+    return bp