Add a Statistics tab with a card for every soundtrack

Part of #41. The top bar has Quiz and Statistics tabs instead of the
Statistics button. The Statistics tab replaces the quiz below the top bar
(the song keeps playing) and shows every soundtrack as a card with its
plays, last played date and most and least played songs, loaded from the
new GET /api/v1/statistics/soundtracks. The cards can be searched (with
the Search popup's matching, now in SoundtrackSearch), filtered on played
or never played, and sorted A-Z, Z-A, most or least played. Clicking a
card opens a popup with all its songs.

Screenshots of the other states only differ in the top bar, and the
layout baseline is taken again with the new statistics states.

main/MainWindow.tscn

@@ -9,6 +9,8 @@
 [ext_resource type="PackedScene" uid="uid://btupbowehiyyu" path="res://popups/QRPopup.tscn" id="15_qr_window"]
 [ext_resource type="PackedScene" uid="uid://cp54idaudb8dp" path="res://popups/AboutPopup.tscn" id="16_about_window"]
 [ext_resource type="PackedScene" uid="uid://bijh5h5yrivm3" path="res://popups/LogPopup.tscn" id="14_26rwn"]
+[ext_resource type="PackedScene" path="res://statistics/StatisticsView.tscn" id="statistics_view_scene"]
+[ext_resource type="PackedScene" path="res://popups/SoundtrackStatsPopup.tscn" id="soundtrack_stats_popup_scene"]
 
 [node name="MainWindow" type="Control" unique_id=407149696]
 layout_mode = 3
@@ -33,6 +35,10 @@ theme_type_variation = &"WindowBackground"
 
 [node name="Quiz" parent="." unique_id=1357908642 instance=ExtResource("quiz_scene")]
 
+[node name="StatisticsView" parent="." unique_id=1212999001 instance=ExtResource("statistics_view_scene")]
+visible = false
+layout_mode = 1
+
 [node name="SearchPopup" parent="." unique_id=1661250375 instance=ExtResource("9_5ijvr")]
 visible = false
 layout_mode = 1
@@ -68,29 +74,6 @@ offset_top = 160.0
 offset_right = 1262.0
 offset_bottom = 860.0
 
-[node name="StatisticsPopupPanel" type="PopupPanel" parent="." unique_id=298311407]
-oversampling_override = 1.0
-initial_position = 2
-size = Vector2i(450, 100)
-
-[node name="Label" type="Label" parent="StatisticsPopupPanel" unique_id=548316493]
-offset_left = 4.0
-offset_top = 4.0
-offset_right = 446.0
-offset_bottom = 96.0
-text = "Statistics"
-horizontal_alignment = 1
-
-[node name="StatisticsLabel" type="Label" parent="StatisticsPopupPanel" unique_id=58226477]
-unique_name_in_owner = true
-offset_left = 4.0
-offset_top = 4.0
-offset_right = 446.0
-offset_bottom = 96.0
-text = "Total amount of soundtracks in the playlist: 9000"
-horizontal_alignment = 1
-vertical_alignment = 1
-
 [node name="AboutPopup" parent="." unique_id=141261008 instance=ExtResource("16_about_window")]
 unique_name_in_owner = true
 visible = false
@@ -108,3 +91,11 @@ offset_left = 562.0
 offset_top = 132.0
 offset_right = 1262.0
 offset_bottom = 832.0
+
+[node name="SoundtrackStatsPopup" parent="." unique_id=1213999001 instance=ExtResource("soundtrack_stats_popup_scene")]
+visible = false
+layout_mode = 1
+offset_left = 610.0
+offset_top = 140.0
+offset_right = 610.0
+offset_bottom = 140.0