Update keybindings and enhance loading screen functionality

- Refactor keybindings for gas spawning across multiple configurations
- Implement new loading screen updates during game initialization
- Add tests to ensure all weapon actions are exposed in keybinding profiles
- Introduce new assets for explosion effects

logs/launcher.log

@@ -0,0 +1,40 @@
+[mice-launcher] script_dir=/home/enne2/dev/mice
+[mice-launcher] game_dir=/home/enne2/dev/mice
+[mice-launcher] python=/home/enne2/dev/mice/.venv/bin/python
+Game starting...
+Loading map from /home/enne2/dev/mice/assets/Rat/level.dat (level 0)
+Loaded profile: Player1
+Screen size: 1280x1280
+[input] no joystick detected
+[input] keybindings profile=pc source=keybindings_pc.yaml reason=default
+[gfx] load_assets requested: level=1 theme=1
+Loading graphics assets...
+Pre-generating blood stain pool...
+[gfx] common assets loaded
+Loading theme assets 1...
+[gfx] theme cache miss -> loaded theme 1
+[flow] start_game: level=1 difficulty=easy starting_rats=5 rat_speed=100%
+[audio] level 1 music=Clockwork_Thicket.mp3 source=config
+[flow] choose_start computed 279 spawnable cells
+[flow] spawn_rat using position=(27, 16)
+[flow] spawn_rat using position=(30, 6)
+[flow] spawn_rat using position=(10, 14)
+[flow] spawn_rat using position=(1, 30)
+[flow] spawn_rat using position=(20, 30)
+[gfx] generating background texture for level=1 theme=1
+[flow] reset_game called: game_end=(False, None) game_status=start_menu menu_screen=start points=0 level=1
+[flow] reset_game -> leaving menu_screen=start and entering gameplay
+[flow] load_level requested: target_level=1 preserve_points=False show_menu=False menu_screen=None current_points=0 next_theme=1
+[audio] level 1 music=Clockwork_Thicket.mp3 source=config
+[flow] theme unchanged: reusing theme 1
+[flow] points reset for new run
+[flow] spawning 5 rats for level=1 difficulty=easy
+[flow] choose_start computed 279 spawnable cells
+[flow] spawn_rat using position=(8, 26)
+[flow] spawn_rat using position=(27, 19)
+[flow] spawn_rat using position=(10, 10)
+[flow] spawn_rat using position=(27, 11)
+[flow] spawn_rat using position=(6, 26)
+[flow] level loaded directly into gameplay: level=1 points=0
+[gfx] generating background texture for level=1 theme=1
+BOOM