refactor: parse plugin service rows into typed shapes

[Abdulmumin1]

Description

Scope: a focused #435 slice that replaces loose plugin-service row/JSON handling with parsed typed shapes at the DB boundary, then updates the plugin settings page consumer to use the new activity shape.

Refs #435

Changes

• Parse plugin rows, stats rows, activity rows, hook rows, and route rows in PluginService with Zod instead of passing loose DB values through the service layer
• Add unit coverage for typed plugin parsing, numeric coercion, structured activity details, and invalid settings payload rejection
• Add a Playwright regression test that saves cache plugin settings and verifies the Activity tab still renders a readable entry

Testing

Unit Tests

• Added/updated unit tests
• All unit tests passing

Commands run:

• npm run type-check --workspace=@sonicjs-cms/core
• npm test --workspace=@sonicjs-cms/core -- plugin-service.test.ts

E2E Tests

• Added/updated E2E tests
• All E2E tests passing

Commands run:

• npx playwright test tests/e2e/63-plugin-settings-activity.spec.ts --config=tests/playwright.config.ts

Screenshots/Videos

• None

Checklist

• Code follows project conventions
• Tests added/updated
• Type checking passes
• No new console errors introduced by this change
• Full E2E suite passing
• Documentation updated (not needed)