feat: block feed submission and subscriptions until user email is verified

[aminamos]

Summary:

Resolves #155.
Restricts feed creation, editing, and notification subscriptions for accounts whose email has not yet been verified, prompting verification with inline alerts.

Expected behavior:

Unverified users see a verification banner and disabled action buttons with tooltips on contribute and notification pages.

Testing tips:

1. Checkout feat/155-block-actions-unverified-email.
2. Run yarn test.
3. Test actions with an unverified session in dev emulator.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with yarn test to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

[vercel]

@aminamos is attempting to deploy a commit to the MobilityData Team on Vercel.

A member of the Team first needs to authorize it.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}