Add Nix development environment and Docker builds

.claude/skills/add-admin-api-endpoint/SKILL.md

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+---
+name: Add Admin API Endpoint
+description: Add a new endpoint or endpoints to Ghost's Admin API at `ghost/api/admin/**`.
+---
+
+# Create Admin API Endpoint
+
+## Instructions
+
+1. If creating an endpoint for an entirely new resource, create a new endpoint file in `ghost/core/core/server/api/endpoints/`. Otherwise, locate the existing endpoint file in the same directory.
+2. The endpoint file should create a controller object using the JSDoc type from (@tryghost/api-framework).Controller, including at minimum a `docName` and a single endpoint definition, i.e. `browse`. 
+3. Add routes for each endpoint to `ghost/core/core/server/web/api/endpoints/admin/routes.js`.
+4. Add basic `e2e-api` tests for the endpoint in `ghost/core/test/e2e-api/admin` to ensure the new endpoints function as expected.
+5. Run the tests and iterate until they pass: `cd ghost/core && yarn test:single test/e2e-api/admin/{test-file-name}`.
+
+## Reference
+For a detailed reference on Ghost's API framework and how to create API controllers, see [reference.md](reference.md).