feat: add PDF reports, timezone management, GPS QR codes, and fix GPS tracking gaps

Issue #1: QR button on GPS Devices tab for re-enrollment
Issue #2: App-wide timezone setting with TimezoneContext, useFormattedDate hook,
  and admin timezone selector. All date displays now respect the configured timezone.
Issue #3: PDF export for Accountability Roster using @react-pdf/renderer with
  professional styling matching VIPSchedulePDF. Added Signal send button.
Issue #4: Fixed GPS "teleporting" gaps - syncPositions now fetches position history
  per device instead of only latest position. Changed cron to every 30s, added
  unique constraint on deviceId+timestamp for deduplication, lowered min interval to 10s.

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

frontend/src/lib/journeyUtils.ts

@@ -0,0 +1,118 @@
+import { Flight, Journey, Layover, LayoverRiskLevel } from '@/types';
+
+function getEffectiveArrival(flight: Flight): Date | null {
+  const t = flight.actualArrival || flight.estimatedArrival || flight.scheduledArrival;
+  return t ? new Date(t) : null;
+}
+
+function getEffectiveDeparture(flight: Flight): Date | null {
+  const t = flight.actualDeparture || flight.estimatedDeparture || flight.scheduledDeparture;
+  return t ? new Date(t) : null;
+}
+
+function computeLayoverRisk(effectiveMinutes: number, scheduledMinutes: number): LayoverRiskLevel {
+  if (effectiveMinutes < 0) return 'missed';
+  if (effectiveMinutes < 30) return 'critical';
+  if (effectiveMinutes < 60) return 'warning';
+  if (scheduledMinutes > 0) return 'ok';
+  return 'none';
+}
+
+function computeLayover(arriving: Flight, departing: Flight, index: number): Layover {
+  const scheduledArr = arriving.scheduledArrival ? new Date(arriving.scheduledArrival) : null;
+  const scheduledDep = departing.scheduledDeparture ? new Date(departing.scheduledDeparture) : null;
+  const effectiveArr = getEffectiveArrival(arriving);
+  const effectiveDep = getEffectiveDeparture(departing);
+
+  const scheduledMinutes = scheduledArr && scheduledDep
+    ? (scheduledDep.getTime() - scheduledArr.getTime()) / 60000
+    : 0;
+
+  const effectiveMinutes = effectiveArr && effectiveDep
+    ? (effectiveDep.getTime() - effectiveArr.getTime()) / 60000
+    : scheduledMinutes;
+
+  return {
+    airport: arriving.arrivalAirport,
+    afterSegmentIndex: index,
+    scheduledMinutes: Math.round(scheduledMinutes),
+    effectiveMinutes: Math.round(effectiveMinutes),
+    risk: computeLayoverRisk(effectiveMinutes, scheduledMinutes),
+  };
+}
+
+function computeEffectiveStatus(flights: Flight[]): { effectiveStatus: string; currentSegmentIndex: number } {
+  // Critical statuses on any segment take priority
+  for (let i = 0; i < flights.length; i++) {
+    const s = flights[i].status?.toLowerCase();
+    if (s === 'cancelled' || s === 'diverted' || s === 'incident') {
+      return { effectiveStatus: s, currentSegmentIndex: i };
+    }
+  }
+
+  // Find first non-terminal segment (the "active" one)
+  for (let i = 0; i < flights.length; i++) {
+    const s = flights[i].status?.toLowerCase();
+    const isTerminal = s === 'landed' || !!flights[i].actualArrival;
+    if (!isTerminal) {
+      return { effectiveStatus: s || 'scheduled', currentSegmentIndex: i };
+    }
+  }
+
+  // All segments landed
+  const last = flights.length - 1;
+  return { effectiveStatus: flights[last].status?.toLowerCase() || 'landed', currentSegmentIndex: last };
+}
+
+export function groupFlightsIntoJourneys(flights: Flight[]): Journey[] {
+  const byVip = new Map<string, Flight[]>();
+  for (const flight of flights) {
+    const group = byVip.get(flight.vipId) || [];
+    group.push(flight);
+    byVip.set(flight.vipId, group);
+  }
+
+  const journeys: Journey[] = [];
+
+  for (const [vipId, vipFlights] of byVip) {
+    // Sort chronologically by departure time, then segment as tiebreaker
+    const sorted = [...vipFlights].sort((a, b) => {
+      const depA = a.scheduledDeparture || a.flightDate;
+      const depB = b.scheduledDeparture || b.flightDate;
+      const timeDiff = new Date(depA).getTime() - new Date(depB).getTime();
+      if (timeDiff !== 0) return timeDiff;
+      return a.segment - b.segment;
+    });
+
+    const layovers: Layover[] = [];
+    for (let i = 0; i < sorted.length - 1; i++) {
+      layovers.push(computeLayover(sorted[i], sorted[i + 1], i));
+    }
+
+    const { effectiveStatus, currentSegmentIndex } = computeEffectiveStatus(sorted);
+
+    journeys.push({
+      vipId,
+      vip: sorted[0]?.vip,
+      flights: sorted,
+      layovers,
+      effectiveStatus,
+      currentSegmentIndex,
+      hasLayoverRisk: layovers.some(l => l.risk === 'warning' || l.risk === 'critical' || l.risk === 'missed'),
+      origin: sorted[0]?.departureAirport,
+      destination: sorted[sorted.length - 1]?.arrivalAirport,
+      isMultiSegment: sorted.length > 1,
+    });
+  }
+
+  return journeys;
+}
+
+export function formatLayoverDuration(minutes: number): string {
+  if (minutes < 0) return `${Math.abs(minutes)}min late`;
+  const h = Math.floor(minutes / 60);
+  const m = minutes % 60;
+  if (h === 0) return `${m}min`;
+  if (m === 0) return `${h}h`;
+  return `${h}h ${m}min`;
+}

frontend/src/lib/utils.ts

@@ -5,16 +5,17 @@ export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));
 }
 
-export function formatDate(date: string | Date): string {
+export function formatDate(date: string | Date, timeZone?: string): string {
   const d = typeof date === 'string' ? new Date(date) : date;
   return d.toLocaleDateString('en-US', {
     year: 'numeric',
     month: 'short',
     day: 'numeric',
+    ...(timeZone && { timeZone }),
   });
 }
 
-export function formatDateTime(date: string | Date): string {
+export function formatDateTime(date: string | Date, timeZone?: string): string {
   const d = typeof date === 'string' ? new Date(date) : date;
   return d.toLocaleString('en-US', {
     year: 'numeric',
@@ -22,13 +23,15 @@ export function formatDateTime(date: string | Date): string {
     day: 'numeric',
     hour: '2-digit',
     minute: '2-digit',
+    ...(timeZone && { timeZone }),
   });
 }
 
-export function formatTime(date: string | Date): string {
+export function formatTime(date: string | Date, timeZone?: string): string {
   const d = typeof date === 'string' ? new Date(date) : date;
   return d.toLocaleTimeString('en-US', {
     hour: '2-digit',
     minute: '2-digit',
+    ...(timeZone && { timeZone }),
   });
 }