collab attachments, multi-day events, calendar improvements

- Collab buckets sync attachments alongside cards (images/PDFs/audio).
  New /api/collab-attachments endpoint on relay, encrypted at rest,
  bucket-scoped for members.
- CalDAV multi-day events via **Bis:** body field. Calendar renders
  event on every day in range with day counter (1/6, 2/6, ...).
- Calendar preserves month across close/reopen (only jumps to today
  on first open).
- Calendar title: centered nav group with [MM-DD] Mon Y [KW-KW] —
  dimmed brackets, fixed width so nothing wiggles.
- Editor: scratchpad uses custom confirm, autobackup-draft dialog
  replaced with custom styled dialog.
- Scanlines theme feature removed (performance issue).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/js/modules/calendar.js

@@ -88,20 +88,35 @@ function matchesRRule(card, targetDateStr) {
     return false;
 }
 
+function getMultiDayEnd(card) {
+    const m = (card.body || '').match(/\*\*Bis:\*\*\s*(\d{4}-\d{2}-\d{2})/i);
+    return m ? m[1] : null;
+}
+
 function getCardsForDate(ds) {
     const results = [];
     const targetYear = parseInt(ds.substring(0, 4));
     for (const c of state.cards) {
-        if (cardBaseDate(c) === ds) {
+        const base = cardBaseDate(c);
+        if (base === ds) {
             results.push({ ...c, _recurring: false });
-        } else if (c.caldav_rrule && matchesRRule(c, ds)) {
-            const baseYear = parseInt(cardBaseDate(c).substring(0, 4));
+        } else if (base && base < ds) {
+            // Multi-day event: check if ds is within [base..end]
+            const end = getMultiDayEnd(c);
+            if (end && ds <= end) {
+                const startMs = Date.parse(base);
+                const curMs = Date.parse(ds);
+                const dayNum = Math.round((curMs - startMs) / 86400000) + 1;
+                const totalDays = Math.round((Date.parse(end) - startMs) / 86400000) + 1;
+                results.push({ ...c, _recurring: false, _multiDay: { day: dayNum, total: totalDays, isEnd: ds === end } });
+            }
+        }
+        if (c.caldav_rrule && matchesRRule(c, ds)) {
+            const baseYear = parseInt(base.substring(0, 4));
             const rrule = parseRRule(c.caldav_rrule);
             const age = rrule?.FREQ === 'YEARLY' ? targetYear - baseYear : null;
-            results.push({ ...c, _recurring: true, _age: age });
+            if (base !== ds) results.push({ ...c, _recurring: true, _age: age });
         } else if ((c.tags || '').split(',').includes('geburtstag')) {
-            // Local birthday cards repeat yearly without RRULE
-            const base = cardBaseDate(c);
             if (base.substring(5) === ds.substring(5) && ds !== base) {
                 const age = targetYear - parseInt(base.substring(0, 4));
                 results.push({ ...c, _recurring: true, _age: age > 0 ? age : null });
@@ -146,7 +161,25 @@ function clearCalHover() {
 }
 
 function render() {
-    title.textContent = `${MONTHS[state.calMonth]} ${state.calYear}`;
+    // Format: [MM-DD] Mon Y [KW-KW]
+    //   MM-DD  = today's month-day
+    //   Mon Y  = displayed month + year (abbreviated)
+    //   KW-KW  = ISO week range spanning the displayed month
+    const isoWeek = (y, m, d) => {
+        const dt = new Date(Date.UTC(y, m, d));
+        const dayNum = dt.getUTCDay() || 7;
+        dt.setUTCDate(dt.getUTCDate() + 4 - dayNum);
+        const yearStart = new Date(Date.UTC(dt.getUTCFullYear(), 0, 1));
+        return Math.ceil((((dt - yearStart) / 86400000) + 1) / 7);
+    };
+    const pad = n => String(n).padStart(2, '0');
+    const nowDate = new Date();
+    const todayMd = `${pad(nowDate.getMonth() + 1)}-${pad(nowDate.getDate())}`;
+    const monAbbr = MONTHS[state.calMonth].substring(0, 3);
+    const lastDay = new Date(state.calYear, state.calMonth + 1, 0).getDate();
+    const wStart = isoWeek(state.calYear, state.calMonth, 1);
+    const wEnd = isoWeek(state.calYear, state.calMonth, lastDay);
+    title.innerHTML = `<span style="color:var(--t-dim)">[${todayMd}]</span> ${monAbbr} ${state.calYear} <span style="color:var(--t-dim)">[${pad(wStart)}-${pad(wEnd)}]</span>`;
 
     const firstDay = new Date(state.calYear, state.calMonth, 1).getDay(); // 0=Sun
     const startOffset = (firstDay + 6) % 7; // Mon=0
@@ -210,9 +243,11 @@ function render() {
             const calCfg = getCardCalConfig(c);
             const itemColor = calCfg?.color || c.color;
             const itemIcon = calCfg?.icon || null;
+            const md = c._multiDay;
             html += `<div class="cal-item" data-card-id="${c.id}" style="border-left-color:${itemColor};">`;
             if (itemIcon) html += `<i class="ph ph-${itemIcon}" style="font-size:9px;color:${itemColor};flex-shrink:0;"></i>`;
-            if (timeStr) html += `<span style="font-family:var(--t-font-pixel);font-size:8px;color:var(--t-dim);flex-shrink:0;">${timeStr}</span>`;
+            if (md) html += `<span style="font-family:var(--t-font-pixel);font-size:8px;color:${itemColor};flex-shrink:0;">${md.day}/${md.total}</span>`;
+            else if (timeStr) html += `<span style="font-family:var(--t-font-pixel);font-size:8px;color:var(--t-dim);flex-shrink:0;">${timeStr}</span>`;
             if (c._recurring && !itemIcon) html += `<i class="ph ph-arrows-clockwise" style="font-size:8px;color:var(--t-dim);flex-shrink:0;"></i>`;
             html += `<span class="truncate">${esc(name)}</span>`;
             html += `</div>`;
@@ -494,9 +529,14 @@ export function refreshCalendar() {
 }
 
 export function openCalendar() {
-    const now = new Date();
-    state.calYear = now.getFullYear();
-    state.calMonth = now.getMonth();
+    // Only jump to today on first open — preserve the user's navigation
+    // when the calendar is re-opened (e.g. after saving a card in a
+    // different month).
+    if (state.calYear == null || state.calMonth == null) {
+        const now = new Date();
+        state.calYear = now.getFullYear();
+        state.calMonth = now.getMonth();
+    }
     render();
     overlay.classList.add('open');
     overlay.style.visibility = '';