Add community testimonial submission form

[SaharPak]

Problem

The Testimonials section (TestimonialsSection.tsx) displays hardcoded testimonials from src/data/testimonials.ts. Community members should be able to submit their own testimonials about how Tech Immigrants helped them.

Goal

Add a "Share your story" form below the existing testimonials so community members can submit their own experience. Submitted testimonials would be reviewed before being displayed.

Suggested Approach

1. Keep the existing testimonial cards as they are (curated, approved testimonials).
2. Add below the grid a CTA card or form section:
   • Headline: "Share your experience" / "نظر خودت رو بنویس"
   • Fields:
     • Name
     • Role / Title
     • Country (where you live now)
     • Your testimonial (textarea)
     • Optional: avatar upload or link
   • Submit button
3. Form submission: Google Form, Formspree, or console log + toast for now.
4. Moderation note: Show a small message like "Testimonials are reviewed before publishing" so users understand it's curated.

Design Notes

• The submission form should feel like a natural extension of the testimonials section
• Keep the existing card design for displayed testimonials
• The form can be a simpler, single-card layout beneath the grid
• Consider a subtle divider or "+" card in the grid that says "Add yours"

Files to modify

• src/components/landing/TestimonialsSection.tsx
• src/data/testimonials.ts (update with real testimonials when available)

Acceptance Criteria

• Existing testimonials still display correctly
• A submission form is available for new testimonials
• Form validates required fields
• Success feedback on submission (toast)
• Clear moderation notice
• Mobile-responsive