feat(core,app,android,ios): My List, synced, and New badges with new-episode rows

My List is a list of titles to watch later, kept in my-list.json by
title key (pstr-core::mylist) and synced as one list/<key> register per
title, so an add or a removal on one device reaches every other. A list
file that will not parse is never written over: changing the list is
refused instead. It is a filter, a row on the library, a button on the
banner and the title page, and an entry in each tile's menu.

pstr-core::news reads node_first_seen against each share's first crawl,
so a newly added share does not badge its whole library. A title that
arrived in the last two weeks and was never played is New; a series
being watched counts the unwatched episodes that arrived after it was
last played ("3 new"). They fill the tile badge and the "New episodes"
and "Recently added" rows. shelves::home puts every row in one order
for all three apps, and a shelf tile of an airing show shows a
countdown ("Ep 8 · in 2 d").

The bridge gains TitleRecord.on_list and .badge, set_on_list, the
MyList filter, airing_countdown and SyncRecord.list_changed.

ios/ProtonStream/UI/TitleView.swift

@@ -251,6 +251,10 @@ struct TitleView: View {
             .disabled(playlist.isEmpty)
             .padding(.top, 16)
             HStack(spacing: 0) {
+                TitleAction(icon: title.onList ? "checkmark" : "plus", label: "My List") {
+                    model.setOnList(title, !title.onList)
+                }
+                .accessibilityValue(title.onList ? "On My List" : "Not on My List")
                 // Only where it would do something different: an unstarted show
                 // already starts at the beginning.
                 if upNext?.resumeAt != nil || title.watchedCount > 0 {