fix: enhance validation for contact and signup forms

[aayan-rashid]

Description

Fixes

closes #8991
closes #8992

• Added full-name validation to the Contact form.
• Added phone-number validation to the Contact form.
• Added full-name validation to the Sign Up form.
• Improved client-side validation for invalid inputs.

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

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Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

[vercel]

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[retenta-bot]

This pull request addresses important validation issues in the contact and signup forms, which is crucial for maintaining data quality. Similar past decisions, such as fixing dead code in the calculateStreak function, highlight the importance of ensuring that our code functions correctly and efficiently. Thank you for your contributions, and I look forward to your updates!

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

Asset	PR Size	Base Size	Difference	Status
static/chunks/app/contact/page-[hash].js	5.38 KB	5.30 KB	+0.08 KB (+1.60%)	🔴 Regression

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	4999.20 KB	4998.89 KB	+0.31 KB (+0.01%)
Total CSS	354.18 KB	354.18 KB	0 B