fix: complete OPC system implementation

- Add database connection retry logic (3 attempts, 5s delay)
- Add missing database functions: get_task_by_id, get_agent_execution, approve_agent_execution, update_agent_config, update_execution_status
- Complete agent execution approval workflow
- Fix agent executor to handle approved executions
- Fix inefficient task queries (use direct ID lookup)
- Add error action handling in agent executor
- Improve LiteLLM error handling with specific exception types
- Reduce LiteLLM timeout from 60s to 30s
- Fix execution status update to only set started_at once
- Consolidate WebSocket datetime serialization with helper function
- Implement update agent endpoint

dashboard/backend/routers/opc_agents.py

@@ -19,6 +19,7 @@ class AgentUpdate(BaseModel):
 
 class ExecutionApproval(BaseModel):
     approved: bool
+    feedback: Optional[str] = None
 
 
 @router.get("/agents")
@@ -53,8 +54,17 @@ async def update_agent(
 ):
     """Update agent configuration (admin only)"""
     user: User = request.state.user
-    # This would need an update_agent function in opc_db
-    raise HTTPException(status_code=501, detail="Not implemented yet")
+    try:
+        agent = await opc_db.update_agent_config(
+            agent_id=agent_id,
+            name=updates.name,
+            description=updates.description,
+            system_prompt=updates.system_prompt,
+            enabled=updates.enabled
+        )
+        return agent
+    except ValueError as e:
+        raise HTTPException(status_code=404, detail=str(e))
 
 
 @router.post("/agents/{agent_id}/execute")
@@ -99,8 +109,7 @@ async def get_execution(
 ):
     """Get execution details"""
     user: User = request.state.user
-    executions = await opc_db.get_agent_executions(limit=1000)
-    execution = next((e for e in executions if e["id"] == execution_id), None)
+    execution = await opc_db.get_agent_execution(execution_id)
     if not execution:
         raise HTTPException(status_code=404, detail="Execution not found")
     return execution
@@ -114,10 +123,13 @@ async def approve_execution(
 ):
     """Approve or reject agent execution (for CxO level actions)"""
     user: User = request.state.user
-    # This would need an approve_execution function in opc_db
-    # For now, return placeholder
-    return {
-        "execution_id": execution_id,
-        "approved": approval.approved,
-        "approved_by": user.username
-    }
+    try:
+        execution = await opc_db.approve_agent_execution(
+            execution_id=execution_id,
+            approved=approval.approved,
+            approved_by=user.username,
+            feedback=approval.feedback
+        )
+        return execution
+    except ValueError as e:
+        raise HTTPException(status_code=404, detail=str(e))