Refactor backend configuration management and update environment settings

- Replace the `config.py` module with a new `settings.py` to streamline environment variable management, focusing on database, CORS, and TURN settings.
- Update references throughout the backend codebase to use the new `settings` module instead of the deprecated `config`.
- Modify the `.env.example` file to reflect the new configuration approach, indicating that model provider credentials should be maintained separately.
- Enhance the `AssistantConfig` model to clarify the source of runtime connection information, ensuring it is injected from model resources rather than relying on defaults from the environment.
- Introduce new user scripts for audio and video management in the Tampermonkey environment, enhancing WebRTC capabilities.

backend/services/config_resolver.py

@@ -1,10 +1,9 @@
 """assistant_id → 运行时配置(把真 key 在服务端组装好)。
 
 浏览器只传 assistant_id;真 key 在这里从 model_resources 取出注入。
-助手按 capability binding 引用资源;取不到则回退该能力默认资源,再回退 .env。
+助手按 capability binding 引用资源;取不到则回退该能力默认资源。
 """
 
-import config
 from db.models import Assistant, AssistantModelBinding, ModelResource
 from models import AssistantConfig
 from sqlalchemy import select
@@ -63,14 +62,14 @@ async def _agent_resource_for(
     ).scalar_one_or_none()
 
 
-def _value(resource: ModelResource | None, key: str, default):
+def _value(resource: ModelResource | None, key: str, default=""):
     if not resource:
         return default
     value = (resource.values or {}).get(key, default)
     return default if value is None else value
 
 
-def _secret(resource: ModelResource | None, key: str, default: str) -> str:
+def _secret(resource: ModelResource | None, key: str, default: str = "") -> str:
     if not resource:
         return default
     return str((resource.secrets or {}).get(key) or default)
@@ -148,19 +147,15 @@ async def resolve_runtime_config(
         agent_interface_type=(agent_resource.interface_type if agent_resource else ""),
         agent_values=(agent_resource.values or {}) if agent_resource else {},
         agent_secrets=(agent_resource.secrets or {}) if agent_resource else {},
-        # 运行时连接信息(真 key + url):模型资源优先,否则 .env 兜底
-        llm_api_key=_secret(llm_resource, "apiKey", config.LLM_API_KEY),
-        llm_base_url=str(_value(llm_resource, "apiUrl", config.LLM_BASE_URL)),
-        vision_llm_api_key=_secret(
-            vision_resource, "apiKey", config.LLM_API_KEY
-        ),
-        vision_llm_base_url=str(
-            _value(vision_resource, "apiUrl", config.LLM_BASE_URL)
-        ),
-        stt_api_key=_secret(stt_resource, "apiKey", config.STT_API_KEY),
-        stt_base_url=str(_value(stt_resource, "apiUrl", config.STT_BASE_URL)),
-        tts_api_key=_secret(tts_resource, "apiKey", config.TTS_API_KEY),
-        tts_base_url=str(_value(tts_resource, "apiUrl", config.TTS_BASE_URL)),
+        # 运行时连接信息(真 key + url):来自模型资源,不再从 .env 兜底。
+        llm_api_key=_secret(llm_resource, "apiKey"),
+        llm_base_url=str(_value(llm_resource, "apiUrl")),
+        vision_llm_api_key=_secret(vision_resource, "apiKey"),
+        vision_llm_base_url=str(_value(vision_resource, "apiUrl")),
+        stt_api_key=_secret(stt_resource, "apiKey"),
+        stt_base_url=str(_value(stt_resource, "apiUrl")),
+        tts_api_key=_secret(tts_resource, "apiKey"),
+        tts_base_url=str(_value(tts_resource, "apiUrl")),
         realtime_api_key=_secret(realtime_resource, "apiKey", ""),
         realtime_base_url=str(_value(realtime_resource, "apiUrl", "")),
     )