fix: register email settings API route (#151)

[NaeemHaque]

Description:

The email settings route file existed but was never registered via injectRoute(), causing the endpoint to return 404 and the admin page to render an empty pipeline
container. Adds error state to the admin UI so fetch failures are visible instead of silently swallowed.

What does this PR do?

The /_emdash/api/settings/email API route file (packages/core/src/astro/routes/api/settings/email.ts) existed but was never registered in
packages/core/src/astro/integration/routes.ts via injectRoute(). This caused the endpoint to return 404, and the admin Email Settings page silently swallowed the error
— showing just the "Email Pipeline" heading with an empty body.

This PR:

1. Registers the missing email settings route in routes.ts
2. Adds fetch error handling to the EmailSettings component so failures display a visible error banner instead of an empty container

Closes #151

Type of change

• Bug fix
• Feature (requires approved Discussion)
• Refactor (no behavior change)
• Documentation
• Performance improvement
• Tests
• Chore (dependencies, CI, tooling)

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm --silent lint:json | jq '.diagnostics | length' returns 0
• pnpm test passes (or targeted tests for my change)
• pnpm format has been run
• I have added/updated tests for my changes (if applicable)
• I have added a changeset (if this PR changes a published package)
• New features link to an approved Discussion: https://github.com/emdash-cms/emdash/discussions/...

AI-generated code disclosure

• This PR includes AI-generated code

Screenshots / test output

Test output:
✓ tests/unit/api/email-settings-route.test.ts (1 test) 9ms

[changeset-bot]

🦋 Changeset detected

Latest commit: c28bb01

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 10 packages

Name	Type
emdash	Patch
@emdash-cms/admin	Patch
@emdash-cms/cloudflare	Patch
@emdash-cms/plugin-ai-moderation	Patch
@emdash-cms/plugin-atproto	Patch
@emdash-cms/plugin-audit-log	Patch
@emdash-cms/plugin-color	Patch
@emdash-cms/plugin-embeds	Patch
@emdash-cms/plugin-forms	Patch
@emdash-cms/plugin-webhook-notifier	Patch

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[github-actions]

All contributors have signed the CLA ✍️ ✅
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[NaeemHaque]

I have read the CLA Document and I hereby sign the CLA