Add an interception app configuration hook before startup

[faresobeid]

InterceptionServer.start() freezes its aiohttp router before returning, so a subclass cannot register additional routes after super().start(). Add a protected _configure_app(app) hook after the built-in routes are registered and before AppRunner.setup() freezes the application.

The default hook is a no-op. Server startup, authentication, tunnel exposure and cleanup remain owned by the existing lifecycle.

Validation: a local HTTP regression fails with 404 before the change and passes afterward. It verifies registration before freeze, exactly one hook call, unchanged authorization on /state, and listener shutdown. The offline suite passed 83 tests; 76 live tests were excluded. Ruff and all-file pre-commit checks passed.

Note

Add interception app configuration hook before startup

Adds an end-to-end test in test_e2e.py that defines an InterceptionServer subclass overriding application configuration before startup. The test verifies the subclass route is reachable after startup, the configured application becomes router-frozen, protected state routes still reject requests, and the server stops accepting connections after shutdown.

^{Macroscope summarized cd47bf9.}