chore: adopt the NAPALM driver standard

- CI moves to .gitea/workflows/ci.yml and calls the shared driver workflow
  of NAPALM/driver-standard; .github/ is gone.
- license = "Apache-2.0" and a LICENSE file: the package declared no
  license at all. README and CHANGELOG.md, py.typed, links to
  git.netork.io, a dev extra with floors; .venv/ and build output ignored.
- Floors on every dependency: napalm-device-types>=4.21.1 (had none),
  napalm>=4.0 (what napalm-device-types needs) and requests>=2.28.0.
  Without them the lowest CI job resolves napalm 0.10, which does not
  build; the tests pass at exactly these floors.
- mypy strict for the package; napalm_yealink.yealink is exempt for now
  (20 errors), recorded in the quality baseline with get_facts'
  complexity. Coverage floor 42 % (measured 42.61 %).

Closes #4

README.md

@@ -0,0 +1,55 @@
+# napalm-yealink
+
+NAPALM driver for Yealink IP phones and video endpoints (T, W, CP and VP series), built on
+[napalm-device-types](https://git.netork.io/NAPALM/napalm-device-types) (`PhoneDriver`).
+
+## Tested against
+
+| Model | Firmware |
+|---|---|
+| not recorded yet | not recorded yet |
+
+## Connection
+
+The phone's REST API under `/api/v1/` over HTTPS on port 443. `open()` logs in at
+`/api/v1/session/login` with the username and the MD5 hex digest of the password (the
+driver computes it) and keeps the session cookie. A refused login does not fail `open()`:
+even without a session, `/api/v1/system/info` names the model and firmware.
+
+```python
+from napalm import get_network_driver
+
+driver = get_network_driver("yealink")
+with driver("192.0.2.20", "admin", "secret") as device:
+    print(device.get_facts())
+```
+
+| Optional argument | Default | Meaning |
+|---|---|---|
+| `verify_ssl` | `False` | verify the phone's TLS certificate |
+
+## Supported
+
+| Getter / action | |
+|---|---|
+| `get_facts` | model, firmware, hostname, serial number from `/api/v1/system/info` |
+| `is_alive` | TCP connect to port 443 |
+
+## Not supported
+
+Everything else a NAPALM driver can offer — interfaces, configuration, LLDP, ARP, MAC
+table, NTP, SNMP, users, routes, `ping` and the CLI — raises `NotImplementedError`.
+`get_facts` reports no uptime and no interfaces.
+
+## Development
+
+The rules are in [STANDARDS.md](https://git.netork.io/NAPALM/driver-standard/src/branch/main/STANDARDS.md).
+
+```bash
+python -m venv .venv && .venv/bin/pip install -e ".[dev]"
+.venv/bin/pytest --cov
+```
+
+## License
+
+Apache-2.0