Title screen, pause menu, settings dialog and savegames

- title screen (continue/new/load/settings/help) and Esc pause menu
- settings: language & sound, camera, graphics, game, rebindable keys;
  stored in localStorage and in every savegame (always applied on load)
- savegames as JSON (.dcsave): download, load via file picker or drag & drop
- autosave to localStorage every 2 minutes and when the tab is hidden/closed
- configurable wall detail, light count, interface size, game speed, hints
- audio behind a cargo feature so native tests run (cargo test --no-default-features)
- savegame round-trip test

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

lang/de.lang

@@ -197,3 +197,72 @@ tile.marked = zum Graben markiert
 # ---- Sprachauswahl
 langsel.title = Sprache
 langsel.hint = Klicke eine Sprache an. Du kannst sie später in den Einstellungen ändern.
+
+# ---- Menüs
+menu.subtitle = Graben. Bauen. Verteidigen. Erobern.
+menu.continue = Fortsetzen
+menu.new = Neues Spiel
+menu.load = Spiel laden
+menu.save = Spiel speichern
+menu.settings = Einstellungen
+menu.help = Hilfe
+menu.resume = Weiterspielen
+menu.main = Hauptmenü
+menu.back = Zurück
+menu.paused = Pause
+menu.drop_hint = Tipp: Du kannst eine .dcsave-Datei auch einfach aufs Spielfenster ziehen, um sie zu laden.
+
+# ---- Einstellungen
+set.tab.sound = Sprache & Ton
+set.tab.camera = Kamera
+set.tab.graphics = Grafik
+set.tab.game = Spiel
+set.tab.keys = Tasten
+set.language = Sprache
+set.volume = Effekt-Lautstärke
+set.music = Musik-Lautstärke
+set.mute = Stumm
+set.rotate_speed = Drehgeschwindigkeit
+set.zoom_speed = Zoomgeschwindigkeit
+set.edge_scroll = Bildschirmrand-Scrollen
+set.invert = Mausdrehung umkehren
+set.outlines = Kachel-Umrisse
+set.wall_detail = Wanddetail
+set.lights = Lichtquellen
+set.ui_scale = Oberflächengröße
+set.game_speed = Spieltempo
+set.hints = Hinweise
+set.keys_hint = Aktion anklicken und Taste drücken. Bereits belegte Tasten werden getauscht.
+set.press_key = Taste drücken für: {0}
+set.esc_cancel = Esc bricht ab
+set.reset_keys = Tasten zurücksetzen
+val.on = An
+val.off = Aus
+val.low = Niedrig
+val.medium = Mittel
+val.high = Hoch
+val.normal = Normal
+val.large = Groß
+
+# ---- Namen der Tastenbelegung
+key.cam_forward = Kamera vor
+key.cam_back = Kamera zurück
+key.cam_left = Kamera links
+key.cam_right = Kamera rechts
+key.rotate_left = Links drehen
+key.rotate_right = Rechts drehen
+key.tilt_up = Neigen hoch
+key.tilt_down = Neigen runter
+key.pause = Pause
+key.mute = Ton an/aus
+key.volume_up = Lauter
+key.volume_down = Leiser
+key.outlines = Kachel-Umrisse
+key.help = Hilfe
+
+# ---- Spielstände
+save.saved = Spiel gespeichert: {0}
+save.loaded = Spiel geladen.
+save.err_invalid = Diese Datei ist kein gültiger DungeonCraft-Spielstand.
+save.err_version = Dieser Spielstand stammt aus einer neueren DungeonCraft-Version.
+save.choose = Spielstand-Datei auswählen ...

lang/en.lang

@@ -198,3 +198,72 @@ tile.marked = marked for digging
 # ---- language selection
 langsel.title = Language
 langsel.hint = Click a language. You can change it later in the settings.
+
+# ---- menus
+menu.subtitle = Dig. Build. Defend. Conquer.
+menu.continue = Continue
+menu.new = New Game
+menu.load = Load Game
+menu.save = Save Game
+menu.settings = Settings
+menu.help = Help
+menu.resume = Resume
+menu.main = Main Menu
+menu.back = Back
+menu.paused = Paused
+menu.drop_hint = Tip: you can also drop a .dcsave file onto the game window to load it.
+
+# ---- settings
+set.tab.sound = Language & Sound
+set.tab.camera = Camera
+set.tab.graphics = Graphics
+set.tab.game = Game
+set.tab.keys = Keys
+set.language = Language
+set.volume = Sound volume
+set.music = Music volume
+set.mute = Mute
+set.rotate_speed = Rotation speed
+set.zoom_speed = Zoom speed
+set.edge_scroll = Screen edge scrolling
+set.invert = Invert mouse rotation
+set.outlines = Tile outlines
+set.wall_detail = Wall detail
+set.lights = Light sources
+set.ui_scale = Interface size
+set.game_speed = Game speed
+set.hints = Hints
+set.keys_hint = Click an action and press a key. Keys already in use are swapped.
+set.press_key = Press a key for: {0}
+set.esc_cancel = Esc cancels
+set.reset_keys = Reset keys
+val.on = On
+val.off = Off
+val.low = Low
+val.medium = Medium
+val.high = High
+val.normal = Normal
+val.large = Large
+
+# ---- key binding names
+key.cam_forward = Camera forward
+key.cam_back = Camera back
+key.cam_left = Camera left
+key.cam_right = Camera right
+key.rotate_left = Rotate left
+key.rotate_right = Rotate right
+key.tilt_up = Tilt up
+key.tilt_down = Tilt down
+key.pause = Pause
+key.mute = Sound on/off
+key.volume_up = Volume up
+key.volume_down = Volume down
+key.outlines = Tile outlines
+key.help = Help
+
+# ---- savegames
+save.saved = Game saved: {0}
+save.loaded = Game loaded.
+save.err_invalid = This file is not a valid DungeonCraft savegame.
+save.err_version = This savegame comes from a newer version of DungeonCraft.
+save.choose = Choose a savegame file ...