Show soundtrack covers and edit alternative names (#49)

Covers: statistics cards show the soundtrack's cover on the left, and the
statistics popup shows it large. Until it arrives, and without a cover, the
soundtrack's initials stand in. Covers load only for cards on or near the
screen, three at a time, and are cached in covers/ next to the settings
(CoverCache), downloaded again only when cover_modified changes. The index and
file handling are shared with CharacterCache in a new FileCache.

Alternative names: the popup shows them and has an editor (add, remove, save)
that sends PUT /soundtracks/{uuid}/alternative-names. The statistics search and
the Search popup find soundtracks by them; Search shows the matching name after
the real one. Search now loads /soundtracks, falling back to the plain list.

The API types are regenerated from the server's spec, with a SoundtrackCover
theme style in every theme.

Closes #49

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

statistics/statistics_view.gd

@@ -5,6 +5,9 @@ extends Panel
 ## cards filtered on whether the soundtrack has been played.
 ##
 ## Shown instead of the quiz when the Statistics tab is chosen.
+##
+## Covers are loaded for the cards on screen as they scroll into view, a few at a time,
+## not for every soundtrack when the tab opens. See [CoverCache].
 
 ## Emitted when a card is clicked, to show all songs of [param soundtrack].
 signal soundtrack_selected(soundtrack: SoundtrackWithSongs)
@@ -19,12 +22,18 @@ enum ShowFilter { ALL, PLAYED, NEVER_PLAYED }
 enum Mode { SOUNDTRACKS, SONGS }
 
 const CARD_SCENE: PackedScene = preload("res://statistics/SoundtrackCard.tscn")
+## How far outside the visible part cards still get their covers, so they are ready when
+## scrolled to.
+const COVER_MARGIN: float = 400.0
 
 ## The cards in the order they are shown, hidden ones included.
 var cards: Array[SoundtrackCard] = []
 ## Whether soundtracks or songs are shown. Change it with [method set_mode].
 var mode: Mode = Mode.SOUNDTRACKS
 
+## The covers on disk, shared by the cards.
+var covers: CoverCache = CoverCache.new()
+
 var _search: SoundtrackSearch = SoundtrackSearch.new()
 var _loading: bool = false
 # The soundtracks last loaded, by name
@@ -61,6 +70,11 @@ func _ready() -> void:
 	sort_option.item_selected.connect(func(_index: int) -> void: apply_sort())
 	retry_button.pressed.connect(refresh)
 	retry_button.visible = false
+	# The cards have moved by the end of the frame
+	card_scroll.get_v_scroll_bar().value_changed.connect(
+			func(_value: float) -> void: load_covers_on_screen.call_deferred())
+	card_scroll.resized.connect(load_covers_on_screen)
+	visibility_changed.connect(load_covers_on_screen)
 
 
 ## Loads the statistics from the server. The cards already shown stay until the new
@@ -108,6 +122,7 @@ func apply_sort() -> void:
 		return _comes_before(a.soundtrack, b.soundtrack, order))
 	for i: int in cards.size():
 		card_grid.move_child(cards[i], i)
+	load_covers_on_screen.call_deferred()
 
 
 ## Shows only the cards or songs that match the search text and the show menu.
@@ -136,6 +151,8 @@ func apply_filter() -> void:
 		count_label.text = "%d soundtracks" % cards.size()
 	else:
 		count_label.text = "%d of %d soundtracks" % [shown, cards.size()]
+	# The grid has moved the cards by the end of the frame
+	load_covers_on_screen.call_deferred()
 
 
 func _on_loaded(soundtracks: Array[SoundtrackWithSongs]) -> void:
@@ -149,19 +166,49 @@ func _on_loaded(soundtracks: Array[SoundtrackWithSongs]) -> void:
 		cards.append(card)
 	while cards.size() > soundtracks.size():
 		cards.pop_back().free()
-	var names: Array[String] = []
 	_soundtracks.clear()
+	var cover_times: Dictionary = {}
 	for i: int in soundtracks.size():
 		cards[i].show_soundtrack(soundtracks[i])
-		names.append(soundtracks[i].soundtrack_name)
 		_soundtracks[soundtracks[i].soundtrack_name] = soundtracks[i]
-	_search.set_names(names)
+		cover_times[soundtracks[i].soundtrack_uuid] = soundtracks[i].cover_modified
+	covers.keep_only(cover_times)
+	_update_search_names()
 	_songs_ready = false
 	apply_sort()
 	if mode == Mode.SOUNDTRACKS:
 		apply_filter()
 
 
+## Asks for the covers of the cards that are on screen, or nearly.
+func load_covers_on_screen() -> void:
+	if !is_visible_in_tree() || mode != Mode.SOUNDTRACKS:
+		return
+	var view: Rect2 = card_scroll.get_global_rect().grow(COVER_MARGIN)
+	for card: SoundtrackCard in cards:
+		if card.visible && view.intersects(card.get_global_rect()):
+			card.load_cover(covers)
+
+
+## Shows the new alternative names of the soundtrack [param updated] and finds it by
+## them, without loading the statistics again.
+func update_alternative_names(updated: Soundtrack) -> void:
+	for soundtrack: SoundtrackWithSongs in _soundtracks.values():
+		if soundtrack.soundtrack_uuid == updated.uuid:
+			soundtrack.alternative_names = updated.alternative_names
+	_update_search_names()
+	apply_filter()
+
+
+func _update_search_names() -> void:
+	var names: Array[String] = []
+	var alternatives: Dictionary = {}
+	for soundtrack: SoundtrackWithSongs in _soundtracks.values():
+		names.append(soundtrack.soundtrack_name)
+		alternatives[soundtrack.soundtrack_name] = soundtrack.alternative_names
+	_search.set_names(names, alternatives)
+
+
 # Typing in the song list waits for a pause, since searching every song takes a moment
 func _on_search_text_changed(_text: String) -> void:
 	if mode == Mode.SONGS: