Add mini-calendar sidebar to Calendar TUI

- Add MonthCalendar widget as a collapsible sidebar (toggle with 's')
- Sidebar syncs with main week grid (week highlight, selected date)
- Click dates in sidebar to navigate week grid to that date
- Click month navigation arrows to change displayed month
- Add goto_date() method to WeekGrid for date navigation

src/calendar/app.py

@@ -18,6 +18,7 @@ from textual.reactive import reactive
 
 from src.calendar.backend import CalendarBackend, Event
 from src.calendar.widgets.WeekGrid import WeekGrid
+from src.calendar.widgets.MonthCalendar import MonthCalendar
 from src.calendar.widgets.AddEventForm import EventFormData
 from src.utils.shared_config import get_theme_name
 
@@ -51,6 +52,26 @@ class CalendarApp(App):
     Screen {
         layout: vertical;
     }
+    
+    #main-content {
+        layout: horizontal;
+        height: 1fr;
+    }
+    
+    #sidebar {
+        width: 26;
+        border-right: solid $surface-darken-1;
+        background: $surface;
+        padding: 1 0;
+    }
+    
+    #sidebar.hidden {
+        display: none;
+    }
+    
+    #sidebar-calendar {
+        height: auto;
+    }
 
     #week-grid {
         height: 1fr;
@@ -98,6 +119,7 @@ class CalendarApp(App):
         Binding("L", "next_week", "Next Week", show=True),
         Binding("g", "goto_today", "Today", show=True),
         Binding("w", "toggle_weekends", "Weekends", show=True),
+        Binding("s", "toggle_sidebar", "Sidebar", show=True),
         Binding("r", "refresh", "Refresh", show=True),
         Binding("enter", "view_event", "View", show=True),
         Binding("a", "add_event", "Add", show=True),
@@ -106,6 +128,7 @@ class CalendarApp(App):
 
     # Reactive attributes
     include_weekends: reactive[bool] = reactive(True)
+    show_sidebar: reactive[bool] = reactive(True)
 
     # Instance attributes
     backend: Optional[CalendarBackend]
@@ -124,7 +147,10 @@ class CalendarApp(App):
     def compose(self) -> ComposeResult:
         """Create the app layout."""
         yield Header()
-        yield WeekGrid(id="week-grid")
+        with Horizontal(id="main-content"):
+            with Vertical(id="sidebar"):
+                yield MonthCalendar(id="sidebar-calendar")
+            yield WeekGrid(id="week-grid")
         yield Static(id="event-detail", classes="hidden")
         yield CalendarStatusBar(id="status-bar")
         yield Footer()
@@ -136,10 +162,23 @@ class CalendarApp(App):
         # Load events for current week
         self.load_events()
 
+        # Sync sidebar calendar with current week
+        self._sync_sidebar_calendar()
+
         # Update status bar and title
         self._update_status()
         self._update_title()
 
+    def _sync_sidebar_calendar(self) -> None:
+        """Sync the sidebar calendar with the main week grid."""
+        try:
+            grid = self.query_one("#week-grid", WeekGrid)
+            calendar = self.query_one("#sidebar-calendar", MonthCalendar)
+            calendar.update_week(grid.week_start)
+            calendar.update_selected(grid.get_cursor_date())
+        except Exception:
+            pass  # Sidebar might not exist yet
+
     def load_events(self) -> None:
         """Load events from backend for the current week."""
         if not self.backend:
@@ -255,11 +294,22 @@ class CalendarApp(App):
     def on_week_grid_week_changed(self, message: WeekGrid.WeekChanged) -> None:
         """Handle week change - reload events."""
         self.load_events()
+        self._sync_sidebar_calendar()
 
     def on_week_grid_event_selected(self, message: WeekGrid.EventSelected) -> None:
         """Handle event selection."""
         self._update_event_detail(message.event)
 
+    # Handle MonthCalendar messages
+    def on_month_calendar_date_selected(
+        self, message: MonthCalendar.DateSelected
+    ) -> None:
+        """Handle date selection from sidebar calendar."""
+        grid = self.query_one("#week-grid", WeekGrid)
+        grid.goto_date(message.date)
+        self.load_events()
+        self._sync_sidebar_calendar()
+
     # Navigation actions (forwarded to grid)
     def action_cursor_down(self) -> None:
         """Move cursor down."""
@@ -311,6 +361,15 @@ class CalendarApp(App):
         mode = "7 days" if self.include_weekends else "5 days (weekdays)"
         self.notify(f"Showing {mode}")
 
+    def action_toggle_sidebar(self) -> None:
+        """Toggle sidebar visibility."""
+        self.show_sidebar = not self.show_sidebar
+        sidebar = self.query_one("#sidebar", Vertical)
+        if self.show_sidebar:
+            sidebar.remove_class("hidden")
+        else:
+            sidebar.add_class("hidden")
+
     def action_refresh(self) -> None:
         """Refresh events from backend."""
         self.load_events()
@@ -383,6 +442,7 @@ Keybindings:
   H/L     - Previous/Next week
   g       - Go to today
   w       - Toggle weekends (5/7 days)
+  s       - Toggle sidebar
   Enter   - View event details
   a       - Add new event
   r       - Refresh