feat: implement pixel-based spaceship animation with 100ms movement duration

Refactor spaceship positioning from column-based to pixel-based coordinates
with time-based interpolation, enabling smooth animation to letter positions
in exactly 100ms regardless of distance. Fixes coordinate mismatch that
prevented spaceship from moving to spawned letters.

src/types.ts

@@ -18,7 +18,7 @@ export const getGamePhase = (status: GameStatus): GamePhase =>
 // Game-Specific Types
 // ============================================================================
 
-export type PlayerPosition = { x: number }; // 0-9 for 10 columns
+export type PlayerPosition = { x: number }; // pixel position 0-800
 export type FallingLetter = {
   id: string;
   letter: string;