Move server calls to MusicServerClient and give players stable ids

Server requests move out of Settings into a new MusicServerClient
autoload with one function per endpoint. It sends requests through a
swappable HttpTransport so tests can fake the server, and it frees its
HTTPRequest nodes after use.

Players now have a UUID that never changes. Their position in
Settings.player_array is only used for the Alt+<number> keybinds.
Previously the position doubled as the id, so removing a player made
points and wins land on the wrong player, and could delete another
player's point from a song.

Also fixes:
- format_time showed 59.6 seconds as "00:60"
- searches containing regex characters such as "Q*bert" broke search
- SongObject and PlayerObject were Nodes that were never freed; they
  are now RefCounted
- search matching is split out of the UI code into find_matches()

SearchWindow.gd

@@ -66,12 +66,18 @@ func perform_search(search_text: String) -> void:
 			child.visible = false
 			label_pool.append(child)
 
+	for soundtrack: String in find_matches(search_text):
+		add_soundtrack_reuse(soundtrack)
+
+## Returns the soundtracks matching [param search_text], best matches first: plain
+## case-insensitive matches, then matches ignoring spaces and special characters,
+## then matches with the letters in order but not next to each other.
+func find_matches(search_text: String) -> Array[String]:
 	var seen: Dictionary = {}
 	var search_text_lower: String = search_text.to_lower()
 	var clean_search_text: String = clean_term(search_text)
 
-	# Collect all matches first, then display in order
-	var matches: Array = []
+	var matches: Array[String] = []
 
 	# Pass 1: Exact case-insensitive contains match on lowercase versions
 	for i in range(precomputed_soundtracks.size()):
@@ -98,9 +104,7 @@ func perform_search(search_text: String) -> void:
 				seen[st_data["original"]] = true
 				matches.append(st_data["original"])
 
-	# Display all matches in the order they appear in soundtracks
-	for soundtrack: String in matches:
-		add_soundtrack_reuse(soundtrack)
+	return matches
 
 # Cleans a term by removing spaces and replacing special characters.
 # Matches MusicServer's clean_term() function.
@@ -113,6 +117,9 @@ func compile_regex_cached(search_term: String) -> RegEx:
 		var regex = RegEx.new()
 		var regText: String = ".*"
 		for letter: String in search_term:
+			# Escape regex metacharacters so searches like "Q*bert" or "(Remix)" work
+			if "\\^$.|?*+()[]{}".contains(letter):
+				regText += "\\"
 			regText += letter + ".*"
 		regex.compile(regText)
 		regex_cache[search_term] = regex
@@ -149,26 +156,28 @@ func get_list_of_soundtracks() -> void:
 	print("get_list_of_soundtracks")
 	var handle_soundtracks: Callable = func handle_soundtracks(array) -> void:
 		if typeof(array) == TYPE_ARRAY:
-			soundtracks = []
-			precomputed_soundtracks = []
 			# Reuse existing labels: hide all and add to pool
 			for child: Label in search_list.get_children():
 				child.visible = false
 				label_pool.append(child)
-			
-			soundtracks.append_array(array)
-			# Precompute cleaned versions for all soundtracks
+			set_soundtracks(array)
 			for soundtrack: String in soundtracks:
-				var cleaned = clean_term(soundtrack)
-				precomputed_soundtracks.append({
-					"original": soundtrack,
-					"lowercase": soundtrack.to_lower(),
-					"cleaned": cleaned
-				})
 				add_soundtrack_reuse(soundtrack)
 		else:
 			print("Unexpected data")
-	Settings.make_request2("/music/all/order", handle_soundtracks, true)
+	MusicServerClient.fetch_all_soundtracks_ordered(handle_soundtracks)
+
+## Replaces the searchable soundtracks and precomputes their search forms.
+func set_soundtracks(list: Array) -> void:
+	soundtracks = []
+	precomputed_soundtracks = []
+	soundtracks.append_array(list)
+	for soundtrack: String in soundtracks:
+		precomputed_soundtracks.append({
+			"original": soundtrack,
+			"lowercase": soundtrack.to_lower(),
+			"cleaned": clean_term(soundtrack)
+		})
 
 func _input(event: InputEvent) -> void:
 	if self.visible == true: