Fix startup URL showing default port instead of configured port

[Christian-Sidak]

Summary

• When uvicorn is launched via CLI with --port N without the PORT environment variable being explicitly set (e.g. using shell default expansion like ${PORT:-3000}), settings.port stays at its default value (8880) while the server actually listens on the CLI-specified port
• The lifespan startup message used settings.port directly, so the Beta Web Player URL showed the wrong port
• Add _get_effective_port() in main.py to inspect sys.argv for --port/--port=/-p arguments, falling back to settings.port when none is found; use it in the startup message

Test plan

• _get_effective_port() returns settings.port when no --port arg is present
• _get_effective_port() returns the CLI value when --port N is passed
• _get_effective_port() handles --port=N (equals form)
• _get_effective_port() handles -p N (short form)
• _get_effective_port() falls back gracefully when --port value is non-integer

Fixes #545

[remsky]

thanks for catching this!

Could we hook uvicorn's "running on" log record instead and print the /web/ link from its args? sys.argv may be a bit fragile here (uvicorn has no -p and I think it misses --host, etc).

[Christian-Sidak]

Good point on sys.argv fragility. Pushed 87e1220: replaced the sys.argv walk with a logging.Handler on uvicorn.error that intercepts the 'running on' record and extracts the port from the bound URL. The lifespan message now just says 'Web Player: enabled (URL logged below)' and the actual link fires when uvicorn logs the socket it opened. This way the displayed port always matches what uvicorn actually bound to, regardless of how it was launched.