Add Python API route miner (#129)

[Dimwiddle]

Description

Implement PythonRouteMiner for Discovery issue #129.

This change adds framework-gated Python route extraction for FastAPI, Flask, and Django using shared discovery context and typed ApiRouteMeta metadata.

What was added

• New miner: src/specleft/discovery/miners/python/routes.py
• Miner wiring/export updates in discovery miner registries
• New miner tests: tests/discovery/miners/test_python_routes.py
• Fixture updates in tests/fixtures/discovery/sample_api.py
• Discovery feature spec updates in features/feature-spec-discovery.md

Type of Change

• New feature
• Tests
• Documentation update

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Testing

• make lint-fix
• make lint
• make test
• make pre-commit

Related Issues

Closes #129