security(supabase): add RLS enablement and policies for users, goals,…

[Nareshkumawat-star]

Summary

Audited database tables and added explicit Supabase Row Level Security (RLS) policies for users, goals, and streak_freezes tables in supabase/schema.sql. Also added documentation in DEVELOPMENT.md explaining RLS policies and how to verify active policies in the Supabase Dashboard.

Closes #3250

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Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that changes existing behavior)
• 📝 Documentation update
• ♻️ Refactor / code cleanup (no functional change)
• ⚡ Performance improvement
• 🔒 Security fix
• 🧪 Tests only

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What Changed

• supabase/schema.sql:
  • Enabled RLS on users, goals, and streak_freezes tables.
  • Added policies restricting user access to their own rows (auth.uid()::text).
• DEVELOPMENT.md:
  • Added documentation on RLS defense-in-depth and dashboard verification instructions.

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How to Test

1. Execute supabase/schema.sql in the Supabase SQL Editor.
2. In the Supabase Dashboard, open Authentication → Policies or Table Editor.
3. Verify that users, goals, and streak_freezes display the RLS Enabled badge and list their user-scoped policies (user_id = auth.uid()::text).

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Checklist

• Linked the related issue above
• Self-reviewed my own diff
• No unnecessary console.log or debug code
• Updated documentation / comments

[github-actions]

GSSoC Label Checklist 🏷️

@Priyanshu-byte-coder — please apply the appropriate labels before merging:

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[Nareshkumawat-star]

Hi @Priyanshu-byte-coder kindly review and merge it