[UIR-027] Add premium settings tab with comparison table

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Outline

Summary

Adds the Premium settings tab, a quiet free versus premium comparison table, and the premium gated Profile View Alert in notifications.

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Changes & Enhancements

• Type of Change:
  • Feature
  • Bugfix
  • Refactor
  • Chore
• Changes:
  • (settings):
    • Add the Premium tab with a regular weight nav entry and #premium deep link support: the free upgrade footer, and the premium plan management state with Manage billing.
    • Make the Account membership row reflect each plan (View plans jumps to the Premium tab on free, Manage billing on premium).
  • (comparison table):
    • Add CompareTable with the seven CMP_ROWS, plain slate blue check marks, and a No dash for features missing on Free.
  • (notifications):
    • Gate Profile View Alert behind premium with a neutral Premium tag that jumps to the Premium tab, and make the Profile Interaction Alert copy premium aware.
  • (i18n):
    • Add English and Japanese copy for the premium tab, comparison rows, and gated alert.

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Page / App Changes

Affected Next.js Routes (Local):

• /[lang]/settings

Before (Screenshot)

After (Screenshot)

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Component / Storybook Changes

Affected Storybook Components (Local):

• Features/Settings/CompareTable > Default
• Features/Settings/SettingsPage > PremiumTabFree
• Features/Settings/SettingsPage > PremiumTabPremium
• Features/Settings/SettingsPage > GatedProfileViewAlert

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.