feat: expand security, background tasks, and dev tooling

[Gautam-7-7]

Summary:

This PR adds a set of core capabilities to the Python SDK:

1. Dependency Injection & Modules:

   • Auto-resolves constructor dependencies via runtime type annotations.
   • Thread-safe singleton instantiation.
   • Circular dependency detection.

2. MCP Primitives & Programmatic Builders:

   • Automatic docstring-based description fallback for @tool and @prompt.
   • Structured validation error responses for MCP JSON-RPC.
   • Programmatic builders (build_tool, build_tools, build_resources, build_prompts, build_controller).

3. Execution Pipeline & Security:

   • Guard, Middleware, Interceptor, Pipe, and Exception Filter execution chain with full context propagation.
   • Standard cryptographic token handling via PyJWT and asynchronous OAuth 2.1 token introspection.
   • SecretValue wrapper, PKCE verification, token stores, and one-line auth setup helpers.

4. Background Tasks & Concurrency:

   • TaskRegistry backed by native asyncio.Task references supporting cancellation.
   • TaskContext exposing abort signal/controller and status lifecycle transitions.
   • Automatic execution of synchronous tool functions in worker thread pools.

5. UI Widgets & Next.js Asset Inlining:

   • Static HTML compilation and asset inlining for serving Next.js widgets without a Node.js production runtime.

6. CLI Scaffolding & Pytest Plugin:

   • CLI support for hot reloading, Claude Desktop registration, and Cursor config integration.
   • Packaged pytest plugin fixture (nitro_client).

Verification & Automated Tests:

• 35/35 pytest unit and integration tests passing

Backward Compatibility:

• Zero breaking changes to existing public decorators (@tool, @resource, @prompt).