feat(ui): re-enable input selection and add context menu

Re-enable user selection for input and textarea elements so users
can select and copy text in form fields. Add an Electron context
menu handler that shows a focused edit menu only for recognized
text input types or editable fields. The menu includes Cut, Copy,
Paste and Select All and respects the editFlags to enable actions.

This restores native editing UX in the renderer while avoiding
global context menus elsewhere in the app.

apps/web/src/styles.scss

@@ -23,6 +23,12 @@ html {
     font-family: Roboto, 'Helvetica Neue', sans-serif;
 }
 
+// Re-enable context menu and text selection for input fields
+input,
+textarea {
+    user-select: text;
+}
+
 @media (display-mode: standalone) {
     body {
         overscroll-behavior-y: contain;