feat: add screen recordings filter, exclude by default

Screen recordings are videos captured by iOS screen recording and are
almost never wanted in a photo backup. They are now excluded from all
counts and backup queues unless explicitly enabled.

Changes:
- BackupFilter.includeScreenRecordings (default: false) added
- PHAssetMediaSubtype.videoScreenRecording predicate applied in both
  fetchAssets() and fetchResultForReconciliation() — excluded at the
  PHFetchRequest level before enumeration
- LocalPhotoIndex.Record.isScreenRecording populated via makeRecord()
  so the fast-path countSafe/count also respects the toggle
- LocalPhotoIndex.passes() checks includeScreenRecordings
- Settings "Screen Recordings" toggle added below Screenshots

This also resolves the transient count flash: screen recordings were
being included in the "need backup" tally on the initial fast-path
reconcile, then dropping when the filter was fully applied.

Co-Authored-By: Kutesir <kutesir@provoc.ug>
Co-Authored-By: Sentry <sentry@provoc.ug>

Features/Settings/SettingsView.swift

@@ -124,6 +124,9 @@ struct SettingsView: View {
                 ToggleRow(icon: "camera.viewfinder", title: "Screenshots",
                           isOn: $store.backupFilter.includeScreenshots)
                 hairline
+                ToggleRow(icon: "record.circle", title: "Screen Recordings",
+                          isOn: $store.backupFilter.includeScreenRecordings)
+                hairline
                 ToggleRow(icon: "rays", title: "RAW",
                           isOn: $store.backupFilter.includeRAW)
                 hairline