Calendar month: drag-to-collapse + full-column selection highlight

Two refinements to get closer to the TickTick reference:
- Drag up on the calendar collapses to the selected week; drag down expands
  to the full month (horizontal swipe still changes month). One direction-
  aware DragGesture handles both axes.
- The selected day now gets a rounded full-column highlight behind its
  number + bars when collapsed (as in the tapped-day screenshot), instead
  of only the day circle.

(Not build-verified — sim runtime removed to reclaim disk.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

KisaniCal/Views/CalendarView.swift

@@ -593,7 +593,8 @@ struct CalendarView: View {
                                 isCurrentMonth: cal.isDate(date, equalTo: displayMonth, toGranularity: .month),
                                 isToday: cal.isDateInToday(date),
                                 isSelected: cal.isDate(date, inSameDayAs: selectedDate),
-                                bars: eventDots(for: date)
+                                bars: eventDots(for: date),
+                                highlightColumn: !monthExpanded && cal.isDate(date, inSameDayAs: selectedDate)
                             )
                             .onTapGesture {
                                 withAnimation(KisaniSpring.snappy) {
@@ -606,9 +607,19 @@ struct CalendarView: View {
                 }
             }
             .padding(.horizontal, 16)
-            .gesture(DragGesture(minimumDistance: 40).onEnded { v in
-                if v.translation.width < -40 { navigateMonth(1) }
-                else if v.translation.width > 40 { navigateMonth(-1) }
+            .gesture(DragGesture(minimumDistance: 30).onEnded { v in
+                let dx = v.translation.width, dy = v.translation.height
+                if abs(dx) > abs(dy) {
+                    // Horizontal swipe → previous/next month
+                    if dx < -40 { navigateMonth(1) }
+                    else if dx > 40 { navigateMonth(-1) }
+                } else {
+                    // Vertical drag → collapse to week (up) / expand to month (down)
+                    withAnimation(KisaniSpring.snappy) {
+                        if dy < -30 { monthExpanded = false }
+                        else if dy > 30 { monthExpanded = true }
+                    }
+                }
             })
 
             // Grabber — expand back to the full month, or collapse to the week.
@@ -1656,6 +1667,7 @@ struct AddCalendarHolidaysView: View {
 struct DayCell: View {
     @Environment(\.colorScheme) private var cs
     let date: Date; let isCurrentMonth: Bool; let isToday: Bool; let isSelected: Bool; let bars: [Color]
+    var highlightColumn: Bool = false
     private let cal = Calendar.current
     var dayNum: String { "\(cal.component(.day, from: date))" }
     /// Locale week-of-year (NOT ISO), intentionally matching the locale-driven grid
@@ -1692,7 +1704,12 @@ struct DayCell: View {
             .padding(.horizontal, 3)
             Spacer(minLength: 0)
         }
+        .padding(.top, 4)
         .frame(maxWidth: .infinity).frame(height: 54).contentShape(Rectangle())
+        .background(
+            RoundedRectangle(cornerRadius: 10)
+                .fill(highlightColumn ? AppColors.text3(cs).opacity(0.12) : .clear)
+        )
     }
 }