[DISC-004] Add saved profiles and favorites

[chev0004]

Outline

Summary

Adds saved profiles so logged-in users can bookmark profiles from discovery and revisit them on a dedicated saved page.

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Changes & Enhancements

• Type of Change:
  • Feature
  • Bugfix
  • Refactor
  • Chore
• Changes:
  • (database):
    • Add saved_profiles table (migration 0003) and data access for saving, unsaving, and listing saved profiles, filtered to still-public profiles.
  • (api):
    • Add POST and DELETE /api/saved with auth and public-profile validation.
  • (discovery):
    • Add a bookmark save/unsave action to profile cards with optimistic state, and prompt logged-out users to log in.
  • (saved page):
    • Add /[lang]/saved listing saved profiles, with an empty state and unsave.
  • (navigation):
    • Add a Saved entry to the user menu.

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Page / App Changes

Affected Next.js Routes (Local):

• /[lang] (discovery cards gain a bookmark action)
• /[lang]/saved (new)

Before (Screenshot)

After (Screenshot)

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Component / Storybook Changes

Affected Storybook Components (Local):

• Discovery > ProfileCard > Save Action

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.