Laser shooters consume energy from the fleet hold when firing (#61)

Mirrors #60's gas bomber ammunition exactly: ENERGY_PER_SHOT (8) drawn
from GameState.fleet_inventory before consuming the firing ship's
cooldown, the button's enabled rule requires affordability too, and an
unaffordable-but-otherwise-ready press still explains itself through a
new LaserStatus label rather than silently doing nothing.

Added two small generic GameState helpers this needed:
deposit_fleet_resource()/deposit_bank_resource(), counterparts to
#60's withdraw_fleet_resource() for resources (energy) with no
dedicated fleet_cargo/fleet_gas_cargo-style property. Along the way,
confirmed deposit_resource_to_building() on a "bank" building deposits
into that building's own per-record inventory, NOT bank_inventory
itself - only building_resource()/building_inventory() special-case
the "bank" capability to redirect there.

test_laser_vessel.gd (#58) updated to stock fleet energy first, since
shots are no longer free - same fix #60 required for the gas bomber's
own pre-existing tests. Also fixed test_laser_vessel.gd's own instance
of the bare-ClassName.CONST script-corruption trap (documented in
#60's commit): var skill: LaserController and a bare
LaserController.BEAM_HALF_WIDTH reference, mirrored into a local const
instead.

Main.tscn

@@ -303,6 +303,22 @@ autowrap_mode = 2
 horizontal_alignment = 1
 text = ""
 
+[node name="LaserStatus" type="Label" parent="UI"]
+mouse_filter = 2
+anchor_left = 1.0
+anchor_right = 1.0
+anchor_top = 1.0
+anchor_bottom = 1.0
+offset_left = -344
+offset_right = -24
+offset_top = -540
+offset_bottom = -490
+theme_override_font_sizes/font_size = 18
+theme_override_colors/font_color = Color(0.3, 0.9, 1, 1)
+autowrap_mode = 2
+horizontal_alignment = 1
+text = ""
+
 [node name="PivotCWButton" type="Control" parent="UI"]
 mouse_filter = 2
 anchor_left = 1.0