feat: add Deepseek config fields and DI wiring (Phase 6)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/.env.example

@@ -5,6 +5,11 @@ LLM_TIMEOUT=60.0
 LLM_ENABLE_THINKING=false
 VLLM_ENGINE=false
 
+# Deepseek API (decompose step only, Package 6)
+DP_BASE_URL=https://api.deepseek.com
+DP_API_KEY=your_deepseek_key_here
+DP_MODEL_NAME=deepseek-v4-pro
+
 EMBEDDING_MODEL=qwen/qwen3-embedding-4b
 EMBEDDING_BASE_URL=https://openrouter.ai/api/v1
 EMBEDDING_API_KEY=

backend/app/core/config.py

@@ -8,13 +8,18 @@ logger = logging.getLogger(__name__)
 
 
 class Settings(BaseSettings):
-    # LLM access
+    # LLM access (OpenRouter / vLLM)
     llm_base_url: str = "https://openrouter.ai/api/v1"
     llm_api_key: str = ""
     llm_model_name: str = "qwen/qwen3.5-35b-a3b"
     llm_enable_thinking: bool = False
     vllm_engine: bool = False
 
+    # Deepseek API (decompose step only, Package 6)
+    dp_base_url: str = "https://api.deepseek.com"
+    dp_api_key: str = ""
+    dp_model_name: str = "deepseek-v4-pro"
+
     # Embeddings
     embedding_model: str = "qwen/qwen3-embedding-4b"
     embedding_base_url: str = "https://openrouter.ai/api/v1"

backend/app/core/dependencies.py

@@ -17,6 +17,12 @@ def get_llm_client():
     return LLMClient(settings)
 
 
+def get_llm_client_dp():
+    settings = get_settings_cached()
+    from app.services.llm_client_dp import LLMClientDP
+    return LLMClientDP(settings)
+
+
 def get_rag_service():
     # Import lazily to avoid circular imports in tests
     from app.services.rag import RAGService