Bring in Godot project + address review feedback (this branch had none of it)

This branch never actually had the Godot scaffold — a workspace-reuse bug
(see agp source repo) let leftover backend/**/__pycache__/*.pyc files from
an unrelated task get swept into this branch's only prior commit, which
was checkpointed under this task's title despite containing zero Godot
files. Removing that garbage and bringing over the real project from
agent/997c429bc6b4 (the original PR's branch) with the review feedback
addressed:

- Play button no longer references the nonexistent scenes/game.tscn.
- Wired PlayButton/QuitButton [connection] entries in main_menu.tscn.
- Removed the invalid uid="uid://main_menu".
- Added .gitignore for .godot/.
- Removed the non-standard [export]/[export_options] sections from
  project.godot (Godot 4 uses export_presets.cfg, not this).

scripts/main_menu.gd

@@ -0,0 +1,14 @@
+extends Control
+
+
+func _ready():
+	pass
+
+
+func _on_play_button_pressed():
+	# No gameplay scene exists yet — wire this to the real scene once one lands.
+	print("Play pressed — no gameplay scene yet")
+
+
+func _on_quit_button_pressed():
+	get_tree().quit()