feat(providers): add Qianfan support

cli/planoai/config_generator.py

@@ -23,6 +23,7 @@ SUPPORTED_PROVIDERS_WITHOUT_BASE_URL = [
     "mistral",
     "openai",
     "xiaomi",
+    "qianfan",
     "gemini",
     "anthropic",
     "together_ai",

cli/planoai/defaults.py

@@ -66,6 +66,12 @@ PROVIDER_DEFAULTS: list[ProviderDefault] = [
         base_url="https://api.deepseek.com/v1",
         model_pattern="deepseek/*",
     ),
+    ProviderDefault(
+        name="qianfan",
+        env_var="QIANFAN_API_KEY",
+        base_url="https://qianfan.baidubce.com/v2",
+        model_pattern="qianfan/*",
+    ),
     ProviderDefault(
         name="mistral",
         env_var="MISTRAL_API_KEY",