feat(console): add self-service account email change flow

[PanAchy]

Issue for this PR

Closes #26363

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds a self-service email change flow for OpenCode Console / Go / Zen accounts.

The flow requires two confirmations:

• the current email confirms the account owner authorized the change
• the new email verifies the destination address

Once both links are confirmed, the canonical auth.email row is updated to the new email. Existing Google/GitHub login identities remain linked to the same account, so the user keeps the same account, workspaces, billing, keys, and usage history.

Changes included:

• adds an email_change Drizzle schema for pending email changes
• adds core email-change request/confirm logic
• adds pure confirmation state tests
• adds an email confirmation template
• adds a confirmation route
• adds an account email change form in workspace settings

A maintainer will need to generate the Drizzle migration because bun run db-dev generate requires SST/Cloudflare credentials.

How did you verify your code works?

Ran:

cd packages/console/core && bun typecheck
cd packages/console/core && bun test test/email-change.test.ts test/date.test.ts test/subscription.test.ts
cd packages/console/app && bun typecheck
cd packages/console/app && bun test test/rateLimiter.test.ts
git diff --check dev...HEAD

The pre-push hook also ran the root typecheck successfully:

bun turbo typecheck

I could not run the full Console auth/DB/mail flow locally because sst shell --stage dev requires maintainer Cloudflare/SST credentials.

I also could not generate the Drizzle migration for the same reason.

Screenshots / recordings

N/A — I could not run the authenticated Console UI locally without maintainer environment credentials.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR