chore(deps): refresh to current, and remove two constraints holding it back

[Jacob-Lasky]

Routine dependency refresh. The deepgram-sdk 6 → 7 major is deliberately not in here — one axis per change, so a failure names its own cause. That's the next PR.

The two constraints that were the actual problem

Both of the stale-pin shape:

• python-dotenv==1.0.0 — an exact pin while 1.2.2 was current. Nothing here touches dotenv internals, so the pin bought nothing and blocked everything. Now >=1.2.2,<2.
• pytest-asyncio<1.0 — held it at 0.26 while 1.4 was current. 1.0 is the release that made asyncio_mode and the loop-scope settings mandatory rather than warned about, and this project already sets all three in [tool.pytest.ini_options]. It was capped below a release it was already compatible with.

Notable resolutions

pytest           8.4.2   -> 9.1.1
pytest-asyncio   0.26.0  -> 1.4.0
starlette        0.52.1  -> 1.3.1
uvicorn          0.41.0  -> 0.51.0
websockets       15.0.1  -> 16.1.1
fastapi          0.135.1 -> 0.140.0
python-socketio  5.14.3  -> 5.16.3
python-multipart 0.0.22  -> 0.0.32
pydantic         2.12.5  -> 2.13.4

Verification

A starlette major and a websockets major are exactly what a unit suite misses, so beyond 113 passed, 1 skipped (warnings down 5 → 2):

• App boots under uvicorn 0.51 / starlette 1.3; GET / returns 200.
• socket.io handshake still negotiates through the ASGI wrapper.
• A real WebSocket handshake completes on websockets 16 (test_wire_contract).
• UI renders; the mode-gating probe passes in both modes, no console errors.