feat(pos): add PIN pad login page with keyboard support and theming

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pos/app.py

@@ -15,6 +15,16 @@ def create_app():
     def health():
         return {'status': 'ok'}
 
+    from flask import render_template, send_from_directory
+
+    @app.route('/pos/login')
+    def pos_login():
+        return render_template('login.html')
+
+    @app.route('/pos/static/<path:filename>')
+    def pos_static(filename):
+        return send_from_directory('static', filename)
+
     return app
 
 if __name__ == '__main__':