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/plugins/collab-buckets/backend.php

@@ -493,6 +493,25 @@ function collabSyncCards(PDO $db): array {
             'push' => $res['updated_at'] ?? $card['updated_at'],
         ]);
         $stats['pushed']++;
+
+        // Push referenced local attachments to the bucket (encrypted,
+        // member-scoped). Extract `uploads/<hex>.<ext>` from the body.
+        $body = $card['body'] ?? '';
+        if ($body && preg_match_all('#uploads/([a-f0-9]+\.\w+)#', $body, $fm)) {
+            foreach (array_unique($fm[1]) as $fn) {
+                $localPath = UPLOAD_DIR . '/' . $fn;
+                if (!is_file($localPath)) continue;
+                $bytes = file_get_contents($localPath);
+                if ($bytes === false) continue;
+                $encoded = collabEncryptPayload(['raw' => base64_encode($bytes)]);
+                if ($encoded === null) continue;
+                collabRelayCall('/api/collab-attachments', 'POST', [
+                    'bucket_uid' => $card['bucket_uid'],
+                    'filename'   => $fn,
+                    'data'       => $encoded,
+                ]);
+            }
+        }
     }
 
     // ── 3. Pull deltas ─────────────────────────────────────
@@ -628,6 +647,28 @@ function collabSyncCards(PDO $db): array {
             ]);
             $stats['pulled']++;
             if ($foreignAuthor) $unreadBuckets[$c['bucket_uid']] = true;
+
+            // Fetch missing attachments referenced in the body.
+            $pulledBody = $fields['body'] ?? '';
+            if ($pulledBody && preg_match_all('#uploads/([a-f0-9]+\.\w+)#', $pulledBody, $fm)) {
+                $uploadDir = UPLOAD_DIR;
+                if (!is_dir($uploadDir)) @mkdir($uploadDir, 0755, true);
+                foreach (array_unique($fm[1]) as $fn) {
+                    $dest = $uploadDir . '/' . $fn;
+                    if (file_exists($dest)) continue; // already have it
+                    $attRes = collabRelayCall('/api/collab-attachments?bucket_uid=' . urlencode($c['bucket_uid']) . '&filename=' . urlencode($fn));
+                    if (!($attRes['ok'] ?? false)) continue;
+                    $atts = $attRes['attachments'] ?? [];
+                    foreach ($atts as $a) {
+                        if (($a['filename'] ?? '') !== $fn) continue;
+                        $decoded = collabDecryptPayload($a['data'] ?? '');
+                        if ($decoded && isset($decoded['raw'])) {
+                            $bytes = base64_decode($decoded['raw']);
+                            if ($bytes !== false) file_put_contents($dest, $bytes);
+                        }
+                    }
+                }
+            }
         }
     } finally {
         // Bump `collab_buckets.updated_at` for every bucket that received

public/plugins/tests/calendar.test.js

@@ -58,4 +58,25 @@ describe('Calendar', () => {
         await sleep(150);
         expect($('#calendar')).toBeHidden();
     });
+
+    it('preserves month across close/reopen', async () => {
+        // Open calendar and navigate forward 3 months
+        click('#calendar-btn');
+        await sleep(200);
+        click('#cal-next');
+        click('#cal-next');
+        click('#cal-next');
+        await sleep(200);
+        const navigatedTitle = $('#cal-title').textContent;
+
+        // Close
+        click('#cal-close');
+        await sleep(150);
+        expect($('#calendar')).toBeHidden();
+
+        // Reopen — must stay on the navigated month, not jump to today
+        click('#calendar-btn');
+        await sleep(200);
+        expect($('#cal-title').textContent).toBe(navigatedTitle);
+    });
 });