feat: implement file upload feature

backend/src/agents/lead_agent/agent.py

@@ -6,6 +6,7 @@ from src.agents.lead_agent.prompt import apply_prompt_template
 from src.agents.middlewares.clarification_middleware import ClarificationMiddleware
 from src.agents.middlewares.thread_data_middleware import ThreadDataMiddleware
 from src.agents.middlewares.title_middleware import TitleMiddleware
+from src.agents.middlewares.uploads_middleware import UploadsMiddleware
 from src.agents.thread_state import ThreadState
 from src.config.summarization_config import get_summarization_config
 from src.models import create_chat_model
@@ -170,6 +171,7 @@ Being proactive with task management demonstrates thoroughness and ensures all r
 
 
 # ThreadDataMiddleware must be before SandboxMiddleware to ensure thread_id is available
+# UploadsMiddleware should be after ThreadDataMiddleware to access thread_id
 # SummarizationMiddleware should be early to reduce context before other processing
 # TodoListMiddleware should be before ClarificationMiddleware to allow todo management
 # ClarificationMiddleware should be last to intercept clarification requests after model calls
@@ -182,7 +184,7 @@ def _build_middlewares(config: RunnableConfig):
     Returns:
         List of middleware instances.
     """
-    middlewares = [ThreadDataMiddleware(), SandboxMiddleware()]
+    middlewares = [ThreadDataMiddleware(), UploadsMiddleware(), SandboxMiddleware()]
 
     # Add summarization middleware if enabled
     summarization_middleware = _create_summarization_middleware()

backend/src/agents/lead_agent/prompt.py

@@ -104,12 +104,16 @@ You have access to skills that provide optimized workflows for specific tasks. E
 </skill_system>
 
 <working_directory existed="true">
-- User uploads: `/mnt/user-data/uploads`
-- User workspace: `/mnt/user-data/workspace`
-  - subagents: `/mnt/user-data/workspace/subagents`
-- Output files: `/mnt/user-data/outputs`
+- User uploads: `/mnt/user-data/uploads` - Files uploaded by the user (automatically listed in context)
+- User workspace: `/mnt/user-data/workspace` - Working directory for temporary files
+- Output files: `/mnt/user-data/outputs` - Final deliverables must be saved here
 
-All temporary work happens in `/mnt/user-data/workspace`. Final deliverables must be copied to `/mnt/user-data/outputs`.
+**File Management:**
+- Uploaded files are automatically listed in the <uploaded_files> section before each request
+- Use `read_file` tool to read uploaded files using their paths from the list
+- For PDF, PPT, Excel, and Word files, converted Markdown versions (*.md) are available alongside originals
+- All temporary work happens in `/mnt/user-data/workspace`
+- Final deliverables must be copied to `/mnt/user-data/outputs` and presented using `present_file` tool
 </working_directory>
 
 <response_style>