add prefilled calendar provider links

src/services/tenderCalendar.js

@@ -40,6 +40,43 @@ export function createTenderICS(t, now = new Date()) {
     'END:VEVENT','END:VCALENDAR',''].map(fold).join('\r\n');
 }
 
+const calendarInstant = date => date.toISOString().replace(/\.000Z$/, 'Z');
+const calendarText = t => [
+  `İKN: ${t.ikn || t.id || ''}`,
+  t.kurum || '',
+  'Kaynak sürümünü ve ihale tarihini resmi kaynaktan doğrulayın.',
+].filter(Boolean).join('\n');
+
+/** Google Calendar'a kaynak tarihiyle ön-doldurulmuş etkinlik taslağı açar. */
+export function googleCalendarUrl(t) {
+  const start = tenderDeadline(t);
+  const instant = calendarInstant(start).replace(/[-:]/g, '');
+  const params = new URLSearchParams({
+    action: 'TEMPLATE',
+    text: `İhale son teklif: ${t.baslik || t.ikn || 'İhale'}`,
+    dates: `${instant}/${instant}`,
+    details: calendarText(t),
+    location: t.ihaleYeri || t.teslimYeri || '',
+  });
+  return `https://calendar.google.com/calendar/render?${params}`;
+}
+
+/** Outlook web takviminde kaynak tarihiyle ön-doldurulmuş taslak açar. */
+export function outlookCalendarUrl(t) {
+  const start = tenderDeadline(t);
+  const instant = calendarInstant(start);
+  const params = new URLSearchParams({
+    path: '/calendar/action/compose',
+    rru: 'addevent',
+    startdt: instant,
+    enddt: instant,
+    subject: `İhale son teklif: ${t.baslik || t.ikn || 'İhale'}`,
+    body: calendarText(t),
+    location: t.ihaleYeri || t.teslimYeri || '',
+  });
+  return `https://outlook.live.com/calendar/0/deeplink/compose?${params}`;
+}
+
 function parseICSDate(value, params = '') {
   const raw = String(value || '').trim();
   const match = /^(\d{4})(\d{2})(\d{2})(?:T(\d{2})(\d{2})(\d{2})Z?)?$/.exec(raw);