[PROFILE-007] Persist multiple profile target languages

[chev0004]

Outline

Summary

Persists profile target language arrays in a normalized table and uses them when loading profile editor data, discovery cards, and account exports. Existing single-language profile rows are backfilled and remain as a fallback for compatibility.

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Changes & Enhancements

• Type of Change:
  • Feature
  • Bugfix
  • Refactor
  • Chore
• Changes:
  • Profile data:
    • Add profile_target_languages schema and migration with ordered rows, unique constraints, and legacy backfill.
    • Update profile and onboarding saves to persist the full target-language list.
  • Profile reads:
    • Load persisted target languages for the profile editor, discovery mapping, and account export with legacy-column fallback.

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Page / App Changes

Affected Next.js Routes (Local):

• /[lang]/profile
• /api/profile
• /api/onboarding
• /api/account/export

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)

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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.