fix: use public DNS on phone-hotspot (carrier resolver fails .dev tunnel)

- yaris_uplink configure() keyfile: dns=8.8.8.8;1.1.1.1 + ignore-auto-dns=true
  so the Pi doesn't rely on the phone's DHCP DNS, which failed to resolve
  yaris.ceaf.dev (NameResolutionError) and broke uploads on the hotspot
- test asserts the DNS lines are written to the keyfile

tests/test_yaris_uplink.py

@@ -58,6 +58,8 @@ class UplinkCredentialTest(unittest.TestCase):
         self.assertEqual(mode, 0o600)
         self.assertIn("ssid=My Phone", keyfile)
         self.assertIn("psk=private-password", keyfile)
+        self.assertIn("dns=8.8.8.8;1.1.1.1;", keyfile)
+        self.assertIn("ignore-auto-dns=true", keyfile)
         for call in run_nmcli.call_args_list:
             self.assertNotIn("private-password", call.args)