[Prateep07]

Summary

Refactor nitrostack/core/app.py into focused implementation modules while preserving the existing nitrostack.core.app import surface.

Changes

• Moved server configuration, application metadata helpers, and the mcp_app decorator into app_config.py.
• Extracted schema normalization and tool input parsing into app_schema.py.
• Moved request metadata, authentication, trace, header, and correlation helpers into app_context.py.
• Added app_entries.py for shared tool, resource, and prompt registration records.
• Split application behavior into modules for registration, protocol handlers, definitions, tool invocation and result conversion, resources and prompts, task handling, and startup.
• Added app_runtime.py to compose the implementation mixins into McpApplication and provide McpApplicationFactory.
• Kept app.py as a compatibility facade that re-exports existing imports, including McpApplication, McpApplicationFactory, ServerConfig, mcp_app, and helper names.

Validation

• All resulting app*.py modules are under 500 lines.
• Ruff and Python compilation checks pass.
• Focused application tests pass.
• Full suite: 1,206 passed, 17 skipped, 4 failed. Remaining failures are in generated project and SDK packaging checks.

closes #120