[Monorepo] Remove the root templates/ projects and their CI #1186

Summary

Once the bridge manifest is verified and the standalone replacements pass their checks, remove the template projects from the monorepo per ADR 0029 (#1089). Only templates/template.json and its integrity check remain during the 90-day bridge.

Delete templates/quickstart/, templates/express-js/, templates/fast-api/, and templates/README.md. Remove .github/workflows/ci-template-quickstart.yml, ci-template-express-js.yml, and ci-template-fast-api.yml. Drop the templates/** globs from the python and typescript entries in .github/labeler.yml. Update DEPENDENCY_MANAGEMENT.md (maintenance tiers table, the audit gate table rows for the template workflows, and the "new templates and examples should not be added to Dependabot" note). Repoint the Templates link in README.md and the "SDK templates" step in CONTRIBUTING.md to the standalone repositories under common-grants (common-grants/cg-api-template-express, common-grants/cg-api-template-hono, common-grants/cg-api-template-fastapi).

Depends on: the bridge manifest rewrite, the Getting Started quickstart move, the FastAPI repository, and the Express repository (#332). Hono (#1152) has no monorepo copy and does not gate this deletion ticket. It remains a prerequisite for the language-guide update and, through that ticket, the CLI retirement release.

Acceptance criteria

• Express ([Template] Create an Express.js API template #332) and FastAPI ([Template] Extract and refresh the FastAPI template into a standalone repository #1183) each have recorded verification before their monorepo copies are removed: a named owner and documented maintenance expectations, SDK request and response validation, a generated OpenAPI document, and passing tests against the supported SDK range. Automated contract validation is tracked in [Template] Add automated CommonGrants contract validation to the API template repositories #1239 and does not gate this ticket
• templates/ contains only template.json; the three project directories and templates/README.md are gone
• The three ci-template-*.yml workflows are removed and no workflow references templates/ except the manifest integrity check
• .github/labeler.yml has no templates/** globs
• DEPENDENCY_MANAGEMENT.md no longer describes a templates maintenance tier
• README.md and CONTRIBUTING.md point to the standalone template repositories
• Verified published CLIs still scaffold from the pinned manifest after the removal