feat(calendar): click due-date day to navigate to filtered Reporting view

- CalendarWidget accepts onDateClick prop; due-date cells are clickable
  with pointer cursor, red hover highlight, and updated tooltip
- App.js wires onDateClick: sets calendarFilter state and navigates to
  the Reporting page
- NavDrawer navigation to Reporting clears calendarFilter so it only
  applies on calendar-initiated navigation
- ReportingPage accepts filterDate prop; initializes columnFilters with
  { dueDate: Set([filterDate]) } so the view lands pre-filtered
- Existing Clear Filters button lets the user dismiss the filter normally

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

frontend/src/components/CalendarWidget.js

@@ -16,7 +16,7 @@ function toLocalDateStr(date) {
     return `${y}-${m}-${d}`;
 }
 
-export default function CalendarWidget() {
+export default function CalendarWidget({ onDateClick }) {
     const today    = new Date();
     const todayStr = toLocalDateStr(today);
 
@@ -116,15 +116,19 @@ export default function CalendarWidget() {
                     return (
                         <div
                             key={idx}
-                            title={hasDue ? `${dueCount} finding${dueCount > 1 ? 's' : ''} due` : undefined}
+                            title={hasDue ? `${dueCount} finding${dueCount > 1 ? 's' : ''} due — click to view` : undefined}
+                            onClick={hasDue && onDateClick ? () => onDateClick(dateStr) : undefined}
                             style={{
                                 display: 'flex', flexDirection: 'column', alignItems: 'center',
                                 gap: '2px', padding: '3px 1px',
                                 borderRadius: '4px',
                                 background: isToday ? 'rgba(14,165,233,0.2)' : 'transparent',
                                 border: isToday ? '1px solid rgba(14,165,233,0.5)' : '1px solid transparent',
-                                cursor: hasDue ? 'default' : 'default',
+                                cursor: hasDue ? 'pointer' : 'default',
+                                transition: hasDue ? 'background 0.15s' : undefined,
                             }}
+                            onMouseEnter={hasDue ? (e) => { e.currentTarget.style.background = isToday ? 'rgba(14,165,233,0.35)' : 'rgba(239,68,68,0.15)'; } : undefined}
+                            onMouseLeave={hasDue ? (e) => { e.currentTarget.style.background = isToday ? 'rgba(14,165,233,0.2)' : 'transparent'; } : undefined}
                         >
                             <span style={{
                                 fontSize: '0.7rem', fontFamily: 'monospace', lineHeight: 1,