Enhance credential management and testing functionality

- Introduce new fields for voice, speed, and language in the AssistantConfig and ProviderCredential models to support TTS and ASR configurations.
- Update the database schema and seeding script to accommodate the new fields, ensuring backward compatibility.
- Implement credential testing endpoints and logic to validate OpenAI-compatible credentials, enhancing user experience and reliability.
- Modify frontend components to include new fields in the credential forms and improve connection testing feedback.
- Refactor related services and API interactions to support the new credential testing feature.

backend/schemas.py

@@ -101,8 +101,20 @@ class CredentialUpsert(CamelModel):
     interface_type: InterfaceType = "openai"    # openai/xfyun/dashscope/gemini
     api_url: str = ""
     api_key: str = ""                           # 写时:占位符/空表示不改
+    voice: str = ""                             # TTS
+    speed: float = 1.0                          # TTS
+    language: str = ""                          # ASR
     is_default: bool = False
 
+    @model_validator(mode="after")
+    def _strip_irrelevant_options(self):
+        if self.type != "TTS":
+            self.voice = ""
+            self.speed = 1.0
+        if self.type != "ASR":
+            self.language = ""
+        return self
+
 
 class CredentialOut(CamelModel):
     id: str
@@ -112,4 +124,25 @@ class CredentialOut(CamelModel):
     interface_type: str
     api_url: str
     api_key: str                                # 读时:打码后的值
+    voice: str
+    speed: float
+    language: str
     is_default: bool
+
+
+class CredentialTestRequest(CamelModel):
+    model_id: str
+    type: ModelType
+    interface_type: InterfaceType = "openai"
+    api_url: str
+    api_key: str = ""
+    voice: str = ""
+    speed: float = 1.0
+    language: str = ""
+
+
+class CredentialTestResult(CamelModel):
+    ok: bool
+    latency_ms: int | None = None
+    message: str
+    detail: str = ""