[NP] Add completion animation to puzzle success state

[FrancescFe]

Context

A static success message communicates completion, but it does not fully deliver the emotional reward of solving the puzzle.

Small motion feedback can make the completion moment feel more satisfying, polished, and memorable without adding unnecessary complexity.

Description

Add a lightweight success animation that plays when the puzzle is completed.

The animation should feel smooth, fast, and celebratory while remaining subtle and aligned with the minimalist puzzle experience.

The exact implementation can be decided during development. Possible examples include:

• overlay fade / scale entrance
• tile pulse animation
• connector line highlight animation
• brief sparkle or celebratory accent
• soft haptic feedback (if supported)

The animation should not delay user interaction or feel intrusive.

Acceptance Criteria

• A success animation is triggered when the puzzle is completed
• The animation feels lightweight and does not block the UI for an excessive time
• The animation is visually consistent with the game style
• The animation can run together with the success overlay
• Any optional haptic feedback is subtle and non-intrusive