feat: detect CAPTCHA_REQUIRED in mobile and portal login handlers

Plain-requests login paths (no TLS impersonation) get fingerprinted by
Cloudflare and receive a CAPTCHA_REQUIRED response. Previously this was
swallowed into the generic "login failed: {raw dict}" message. Now it
raises a clear GarminConnectConnectionError that falls through to the
next strategy, with a readable log line instead of a dict dump.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: cyberjunky

garminconnect/client.py

@@ -434,6 +434,12 @@ def _do_mobile_login(self, sess: Any, email: str, password: str) -> None:
         if res.get("error", {}).get("status-code") == "429":
             raise GarminConnectTooManyRequestsError("Mobile login: 429 in JSON body")
 
+        if resp_type == "CAPTCHA_REQUIRED":
+            raise GarminConnectConnectionError(
+                "Mobile login: CAPTCHA required (bot challenge) — "
+                "falling through to next strategy"
+            )
+
         raise GarminConnectConnectionError(f"Mobile login failed: {res}")
 
     # ------------------------------------------------------------------ #
@@ -761,6 +767,12 @@ def _do_portal_web_login(self, sess: Any, email: str, password: str) -> None:
         if res.get("error", {}).get("status-code") == "429":
             raise GarminConnectTooManyRequestsError("Portal login: 429 in JSON body")
 
+        if resp_type == "CAPTCHA_REQUIRED":
+            raise GarminConnectConnectionError(
+                "Portal login: CAPTCHA required (bot challenge) — "
+                "falling through to next strategy"
+            )
+
         raise GarminConnectConnectionError(f"Portal web login failed: {res}")
 
     # ------------------------------------------------------------------ #