feat(advisors): add health advisor support

[jordienr]

Problem

The MCP exposes Security and Performance Advisor findings, but it cannot retrieve the newer Health Advisor findings.

Fix

Add health to the existing get_advisors tool. It runs the v2 Health Advisor checks, returns the established lint shape, and filters dashboard-only sentinel results.

How to test

• Run CI=1 pnpm --filter @supabase/mcp-server-supabase test -- --run src/server.test.ts
• Expected result: 113 tests pass, including the Health Advisor payload, response normalization, project-ref encoding, and malformed-response cases.
• Run pnpm --filter @supabase/mcp-server-supabase typecheck
• Expected result: TypeScript completes without errors.