feat: P2.2 Create Appointment from Email + P2.4 Calendar Dashlet + P2.12 Action Wheel + P2.14 Share Files

- P2.2: 'Create Appointment' button in email viewer → pre-fills event modal
  with subject, body, participants, date. calendar-store newEventPrefill state.
- P2.4: MiniCalendarDashlet in sidebar bottom — month grid with event dots,
  day click navigates to calendar. Collapsible, respect firstDayOfWeek.
- P2.12: Custom radial menu (components/ui/radial-menu.tsx) — circular SVG
  menu with keyboard nav, animations. Wired into email-list, contact-list,
  file-browser, calendar-month-view right-click handlers.
- P2.14: 'Send as Attachment' button in file browser — opens compose tab
  with selected files pre-attached via Pro tab store.

locales/en/common.json

@@ -301,6 +301,7 @@
     "view_source": "View source",
     "export_email": "Export as .eml",
     "forward_as_attachment": "Forward as attachment",
+    "create_appointment": "Create Appointment",
     "import_email": "Import .eml or .zip",
     "keyboard_shortcuts": "Keyboard shortcuts (?)",
     "email_source": "Email Source",
@@ -3080,6 +3081,7 @@
     "delete_confirm_title": "Delete resource",
     "delete_confirm_message": "Are you sure you want to delete \"{name}\"? This cannot be undone.",
     "download": "Download",
+    "send_as_attachment": "Send as Attachment",
     "name": "Name",
     "size": "Size",
     "modified": "Modified",