fix(feedback): remove ball contact screen flash

TODO.md

@@ -17,7 +17,7 @@ The largest gap between this and a AAA-feeling product is presentation, not code
 - [ ] **Audio — there is none.** Zero sound files, zero `AudioStreamPlayer` nodes, no bus layout. Needs: engine hum pitched to throttle, turbo whoosh, ball impacts scaled by collision impulse, wall scrapes, goal explosion, crowd bed, UI clicks, countdown beeps, music. Can be driven off `Ship`'s existing telemetry signals.
 - [x] SSAO/SSIL in the arena Environments — cheapest single perceived-quality win available; grounds the ships against the deck and gives the fillets and goal recesses real depth.
 - [x] VFX on anything that moves: throttle-reactive engine cores and simple rear flames, a speed-scaled ball trail and team-tinted goal bursts.
-- [x] Impact feedback — intensity-scaled screen shake, unscaled hit-stop, HUD flash and controller rumble on ball contact.
+- [x] Impact feedback — intensity-scaled screen shake, unscaled hit-stop and controller rumble on ball contact.
 - [x] Camera feel in `ship_camera.gd` — speed-based FOV widening, turbo kick-back and decaying impact shake.
 - [x] Goal celebration sequence: goal burst, team-tinted flash/title card, dedicated camera cut and slow-motion beat after authoritative score registration and before reset/kickoff.
 - [x] Local lighting / dynamic GI — four local pitch lights plus SDFGI provide bounce and contact lighting for the runtime-generated arena shell; the shader's `hull_fill` stand-in is retired. (The shell is generated in `_ready`, so it cannot participate in an editor LightmapGI bake.)