[PROFILE-009] Align profile and onboarding validation

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Outline

Summary

Profile and onboarding now validate their shared fields through common helpers so the profile form cannot save values the database would reject.

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Changes & Enhancements

• Type of Change:
  • Feature
  • Bugfix
  • Refactor
  • Chore
• Changes:
  • (validation):
    • Add shared field helpers for language code, country, bio, and tags used by both the profile and onboarding schemas
  • (profile):
    • Validate primary and per-row target language codes, validate the country 2-letter shape, trim the bio before length checks, and trim tags before length and duplicate checks
  • (database):
    • Raise the profile tag limit constraint from 6 to 8 so it matches the premium tag cap the form already allows

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Page / App Changes

Affected Next.js Routes (Local):

Before (Screenshot)

After (Screenshot)

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Component / Storybook Changes

Affected Storybook Components (Local):

Before (Screenshot)

After (Screenshot)

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Not Doing

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Other (Remarks)

Includes drizzle migration 0006, which widens the profile tag check constraint; run db:migrate on deploy.

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Checklists

• Code is well-documented (comments, JSDoc, etc.).
• Existing comments were updated as needed.
• No out-of-scope changes are included.
• Write TODO comments where future work is required.
• Removed unnecessary debug code (e.g., console.log, debugger).
• Self-reviewed and tested locally.