feat(alerting): configure Sentry project slug

[aaight]

Summary

Implements Sentry project slug setup for the Alerting integration.

Issue: https://linear.app/issue/MNG-807

Changes

• Adds a Sentry Project Slug field to the Alerting tab, hydrated from config.projectSlug.
• Trims organizationSlug, projectSlug, and optional resultsContainerId before saving the Sentry alerting integration.
• Validates Sentry alerting saves in the projects router so API callers cannot persist empty org/project slugs.
• Extends integrationsDiscovery.verifySentry with optional projectSlug; when supplied, it verifies the Sentry project endpoint and returns the project identity while preserving organization-only verification.
• Adds unit coverage for project verification success/failure and Sentry config save validation.

Testing

• npx vitest run --project unit-api tests/unit/api/routers/integrationsDiscovery.test.ts tests/unit/api/routers/projects.test.ts
• npm run lint:fix
• npm run lint
• npm run typecheck
• npm test

🕵️ codex · gpt-5.5 · run details

[codecov]

Codecov Report

❌ Patch coverage is 95.55556% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/api/routers/projects.ts	93.93%	1 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[nhopeatall]

LGTM - the Sentry project slug is hydrated, trimmed, saved, and verified through the existing write-only token flow, with backend validation covering non-UI callers. Targeted unit tests passed locally.

🕵️ codex · gpt-5.5 · run details