Refresh v4.8.x docs and fix CI, Docker, runtime, and MCP validation

[pozylon]

Stale documentation, permissive CI jobs, broken container layouts, and duplicated MCP enums made the v4.8.x checkout harder to run and maintain. This updates the guides against the implementation and fixes the selected runtime, CI, Docker, and validation issues.

• Refresh repository guides, package API examples, contributor instructions, and code comments. Keep all documentation updates in one atomic commit (185154b3e), followed by the implementation commit (b50b32b2e).
• Require nonmutating lint and successful tests/builds in CI. Fix the Admin UI lint errors and MongoDB test-port collision exposed by these gates; keep scheduler correctness checks in the default suite and make hardware timing benchmarks opt-in.
• Preserve the existing EUPL text under the conventional LICENSE filename and align the docs package license metadata.
• Align package engines, development pins, and Node container stages on Node.js 26.8.2. This raises the minimum supported Node version and is a breaking runtime requirement. Dependency resolutions remain unchanged.
• Repair all eight Dockerfiles to use repository-root contexts and workspace paths, retain required production dependencies, serve static exports with nginx, and check real HTML/GraphQL responses. Exclude local environment overrides and Jenkins credentials from build contexts.
• Derive MCP provider subtypes and order statuses from domain definitions, rejecting removed values and mismatched provider categories.

Validation:

• Linux CI test command: 711 unit tests, 1,017 integration tests, and four healthcheck tests passed; five integration tests remain skipped. The final scheduler test-only adjustment was mounted read-only into the built CI image for this run.
• All four optional scheduler benchmarks passed separately. Scheduler correctness also passed with a CPU quota that reproduced the original timing failures.
• Root/Admin UI lint, package/TypeScript builds, Admin UI production build, and the documentation production build passed.
• All eight container images built. Startup checks passed for docs, Admin UI, minimal, Fastify kitchensink, Express, and ticketing; static checks also covered nested routes, JavaScript assets, and HTTP 404 responses.
• Documentation audit checked relative links, GraphQL examples, and package imports/exports. Original comment-only edits preserved emitted JavaScript.

Known limits: optional @parse/node-apn@8.1.0 declares Node 20/22/24 support, so Apple Wallet push compatibility with Node 26 remains unverified. The OIDC image was built, but its external identity-provider login was not exercised. External payment/storage integrations were not exercised.

Targets v4.8.x. The paused adaptation to v5/master is excluded.