refactor: simplify simulation to run forever as paper trade

- No duration limit - runs forever until user stops
- Only 1 running simulation per bot (returns existing if already running)
- Always paper trade (no auto-execute option)
- Removed Pro upgrade banner
- Removed duration and auto-execute config options
- Simplified API to only require token, chain, check_interval

src/backend/app/api/simulate.py

@@ -124,6 +124,19 @@ async def start_simulation(
             status_code=status.HTTP_403_FORBIDDEN, detail="Not authorized"
         )
 
+    # Check if there's already a running simulation for this bot
+    existing_simulation = (
+        db.query(Simulation)
+        .filter(Simulation.bot_id == bot_id, Simulation.status == "running")
+        .first()
+    )
+    if existing_simulation:
+        # Return existing running simulation
+        if existing_simulation.id in running_simulations:
+            engine = running_simulations[existing_simulation.id]
+            existing_simulation.signals = engine.get_signals()
+        return existing_simulation
+
     settings = get_settings()
     simulation_id = str(uuid.uuid4())
 
@@ -135,9 +148,8 @@ async def start_simulation(
         "bot_id": bot_id,
         "token": config.token,
         "chain": config.chain,
-        "duration_seconds": config.duration_seconds,
         "check_interval": check_interval,
-        "auto_execute": config.auto_execute,
+        "auto_execute": False,  # Always paper trade
         "strategy_config": bot.strategy_config,
         "ave_api_key": settings.AVE_API_KEY,
         "ave_api_plan": settings.AVE_API_PLAN,

src/backend/app/db/schemas.py

@@ -100,9 +100,7 @@ class BacktestResponse(BaseModel):
 class SimulationCreate(BaseModel):
     token: str
     chain: str
-    duration_seconds: int = 3600
     check_interval: int = 60
-    auto_execute: bool = False
 
     @field_validator("chain")
     @classmethod

src/backend/app/services/simulate/engine.py

@@ -59,10 +59,9 @@ class SimulateEngine:
             self.results = {"error": "Token ID is required"}
             return self.results
 
-        end_time = datetime.utcnow().timestamp() + self.duration_seconds
-
+        # Run forever until stopped (no end_time limit)
         try:
-            while self.running and datetime.utcnow().timestamp() < end_time:
+            while self.running:
                 try:
                     price_data = await self.ave_client.get_token_price(token_id)
                     if price_data:
@@ -87,10 +86,8 @@ class SimulateEngine:
                         break
                     await asyncio.sleep(1)
 
-            if self.running:
-                self.status = "completed"
-            else:
-                self.status = "stopped"
+            # Simulation was stopped
+            self.status = "stopped"
 
         except Exception as e:
             self.status = "failed"