Add a reduced-motion guard and accessible labelling to the landing StarField background

[1nonlypiece]

📌 Description

src/components/landing-page/ui/StarField.tsx renders a large decorative
star background. It should not animate for users who prefer reduced motion, must
be hidden from assistive tech as decorative, and should not regress landing-page
performance.

This issue adds a prefers-reduced-motion guard, marks the field as decorative
(aria-hidden), and ensures it does not block interaction or hurt rendering cost.

🎯 Requirements and Context

• Respect prefers-reduced-motion: reduce (disable/limit animation).
• Mark the decorative layer aria-hidden and ensure pointer-events: none.
• Keep render cost bounded (no per-frame layout thrash; CSS over JS where possible).
• No visual regression for default-motion users.

🛠️ Suggested Execution

1. Fork the repo and create a branch

git checkout -b perf/starfield-reduced-motion

2. Implement changes

• Update src/components/landing-page/ui/StarField.tsx with the motion guard and
  ARIA/pointer fixes.
• Add src/components/landing-page/__tests__/StarField.test.tsx covering
  reduced-motion behaviour, aria-hidden, and pointer-events (mock matchMedia).
• Add docs/performance/STARFIELD.md documenting the motion and cost decisions.
• Validate it does not intercept clicks or announce to screen readers.

3. Test and commit

• Run pnpm test.
• Cover edge cases: reduced-motion on/off, SSR (no window), large viewport.

Example commit message

perf: reduced-motion guard and a11y for landing StarField

✅ Guidelines

• Minimum 95% test coverage on new/changed lines.
• Clear, reviewer-friendly documentation.
• Timeframe: 96 hours.

🏷️ Labels

type-performance · type-security · area-frontend · MAYBE REWARDED ·
GRANTFOX OSS · OFFICIAL CAMPAIGN

💬 Community & Support

• Join the CommitLabs contributor Discord to coordinate and get unblocked fast:
  https://discord.gg/WV7tdYkJk
• Introduce yourself before starting so we can avoid duplicate work and pair you
  with a reviewer. Maintainers triage actively and review fast.

[Promzy204-bad]

@Promzy204-bad has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Promzy204-bad to this issue.

[GBOYEE]

I'd like to work on this.

Approach:

• I'll implement the UI changes with proper state handling
• Verify with existing tests + add new ones if needed

Estimated effort: ~1-2 hours. PR incoming shortly.

[GBOYEE]

I'd like to work on this.

Approach:

• I'll implement the UI changes with proper state handling
• Verify with existing tests + add new ones if needed

Estimated effort: ~1-2 hours. PR incoming shortly.

[GBOYEE]

I'd like to work on this issue.

My Approach

• Analyze the root cause of: ##
• Implement a clean, tested fix
• Follow existing code patterns and conventions

Files Likely Modified

• TBD after analysis

Timeline

• Estimated completion: 15-30 minutes
• PR will be submitted with tests and documentation

Closes #655