[codex] add HTTP param decorators

[ItayTheDar]

Summary

• Add PyNest HTTP parameter decorator markers: Body, Param, Query, Headers, Req, Res, Ip, HostParam, createParamDecorator, and ExecutionContext.
• Adapt route registration to rewrite only marked parameters into FastAPI dependencies, preserving existing FastAPI signature binding for undecorated routes.
• Add tests for built-in decorators, custom decorators, pipes, request/response injection, and backwards compatibility.
• Add a documentation page and MkDocs nav entry for the new API.

Notes

Python does not support NestJS-style parameter decorator syntax inside function parameters, so this implements the feature using the existing PyNest/WebSocket-style marker-default pattern, for example def get(self, item_id: int = Param("id")).

Validation

• uv run --group test python -m pytest -q — 162 passed, 8 warnings
• uv run --group docs mkdocs build --strict — exits 0; existing docs warnings remain for Material/MkDocs 2.0 notice and lifespan_tasks.md not being included in nav.