feat(legal): add privacy policy page and acceptance checkbox on registration

[vitorhugo-java]

Summary

• Adds a public /privacy-policy route with a full Privacy Policy page (src/pages/legal/PrivacyPolicy.tsx) covering data collection, Google API usage, cookies, retention, and user rights — written specifically for Applywell to satisfy Google's OAuth2 production approval requirements
• Adds a mandatory Privacy Policy acceptance checkbox to the registration form (src/pages/auth/Register.tsx); the form cannot be submitted without checking it
• Sends acceptedPrivacyPolicy: true in the RegisterPayload to the backend API
• Exposes privacyPolicyAccepted: boolean on the User type (src/types/index.ts)

Why

Google requires a publicly accessible, accurate Privacy Policy before approving an OAuth2 app for production. This change provides that page and ensures every new user explicitly acknowledges it at sign-up time.

Reviewer notes

• The Privacy Policy page is intentionally public (no auth required) so Google's review team and unauthenticated users can access it
• The checkbox uses react-hook-form validation — submitting without checking shows an inline error below the checkbox
• The link to /privacy-policy opens in a new tab so the user doesn't lose their partially filled form
• Backend counterpart: vitorhugo-java/SpringBoot-JobApplyTracker — PR adds privacy_policy_accepted column (Flyway V28) and @AssertTrue validation on RegisterRequest

Test plan

• Navigate to /privacy-policy while logged out — page renders correctly
• Try to register without checking the checkbox — inline error appears, form does not submit
• Check the checkbox and complete registration — succeeds, user lands on dashboard
• Verify the link inside the checkbox opens the policy in a new tab without clearing the form

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