fix: flatten strategy config schema to match engine expectations

LLM was outputting nested params structure but engines expect flat fields.
This caused backtesting and simulation to never trigger any trades.

Changes:
- llm_connector.py: Update prompt to output flat condition structure
- crew.py: Update StrategyValidator to validate flat structure
- crew.py: Update StrategyExplainer to read flat structure

Fixes #25

src/backend/app/db/schemas.py

@@ -1,5 +1,5 @@
-from pydantic import BaseModel, EmailStr
-from typing import Optional, List, Any
+from pydantic import BaseModel, EmailStr, field_validator
+from typing import Optional, List, Any, Dict
 from datetime import datetime
 
 
@@ -69,6 +69,13 @@ class BacktestCreate(BaseModel):
     start_date: str
     end_date: str
 
+    @field_validator("chain")
+    @classmethod
+    def chain_must_be_bsc(cls, v: str) -> str:
+        if v != "bsc":
+            raise ValueError("Phase 1 only supports BSC (bnb chain)")
+        return v
+
 
 class BacktestResponse(BaseModel):
     id: str
@@ -90,6 +97,13 @@ class SimulationCreate(BaseModel):
     check_interval: int = 60
     auto_execute: bool = False
 
+    @field_validator("chain")
+    @classmethod
+    def chain_must_be_bsc(cls, v: str) -> str:
+        if v != "bsc":
+            raise ValueError("Phase 1 only supports BSC (bnb chain)")
+        return v
+
 
 class SimulationResponse(BaseModel):
     id: str

src/backend/app/services/ai_agent/crew.py

@@ -33,29 +33,24 @@ class StrategyValidator:
                 errors.append(f"Condition {i}: unsupported type '{cond_type}'")
                 continue
 
-            params = condition.get("params", {})
             if cond_type in ["price_drop", "price_rise", "volume_spike"]:
-                if "token" not in params:
+                if "token" not in condition:
                     errors.append(f"Condition {i}: missing 'token'")
-                if "threshold_percent" not in params:
-                    errors.append(f"Condition {i}: missing 'threshold_percent'")
-                elif not isinstance(params["threshold_percent"], (int, float)):
-                    errors.append(
-                        f"Condition {i}: 'threshold_percent' must be a number"
-                    )
-                elif params["threshold_percent"] <= 0:
-                    errors.append(
-                        f"Condition {i}: 'threshold_percent' must be positive"
-                    )
+                if "threshold" not in condition:
+                    errors.append(f"Condition {i}: missing 'threshold'")
+                elif not isinstance(condition["threshold"], (int, float)):
+                    errors.append(f"Condition {i}: 'threshold' must be a number")
+                elif condition["threshold"] <= 0:
+                    errors.append(f"Condition {i}: 'threshold' must be positive")
 
             elif cond_type == "price_level":
-                if "token" not in params:
+                if "token" not in condition:
                     errors.append(f"Condition {i}: missing 'token'")
-                if "price" not in params:
+                if "price" not in condition:
                     errors.append(f"Condition {i}: missing 'price'")
-                if "direction" not in params:
+                if "direction" not in condition:
                     errors.append(f"Condition {i}: missing 'direction'")
-                elif params["direction"] not in ["above", "below"]:
+                elif condition["direction"] not in ["above", "below"]:
                     errors.append(
                         f"Condition {i}: direction must be 'above' or 'below'"
                     )
@@ -85,23 +80,22 @@ class StrategyExplainer:
                 explanations.append("This strategy will trigger when:")
                 for cond in cond_list:
                     cond_type = cond.get("type")
-                    params = cond.get("params", {})
-                    token = params.get("token", "the token")
+                    token = cond.get("token", "the token")
 
                     if cond_type == "price_drop":
-                        pct = params.get("threshold_percent", 0)
+                        pct = cond.get("threshold", 0)
                         explanations.append(f"  - {token} price drops by {pct}%")
                     elif cond_type == "price_rise":
-                        pct = params.get("threshold_percent", 0)
+                        pct = cond.get("threshold", 0)
                         explanations.append(f"  - {token} price rises by {pct}%")
                     elif cond_type == "volume_spike":
-                        pct = params.get("threshold_percent", 0)
+                        pct = cond.get("threshold", 0)
                         explanations.append(
                             f"  - {token} trading volume increases by {pct}%"
                         )
                     elif cond_type == "price_level":
-                        price = params.get("price", 0)
-                        direction = params.get("direction", "unknown")
+                        price = cond.get("price", 0)
+                        direction = cond.get("direction", "unknown")
                         explanations.append(
                             f"  - {token} price crosses {direction} ${price}"
                         )

src/backend/app/services/ai_agent/llm_connector.py

@@ -61,9 +61,9 @@ class MiniMaxConnector:
         system_prompt = """You are a trading strategy designer. Parse the user's natural language request into a JSON strategy_config object.
 
 Supported conditions (MVP):
-- price_drop: Token price drops by X% (requires: token, threshold_percent)
-- price_rise: Token price rises by X% (requires: token, threshold_percent)
-- volume_spike: Trading volume increases X% (requires: token, threshold_percent)
+- price_drop: Token price drops by X% (requires: token, threshold)
+- price_rise: Token price rises by X% (requires: token, threshold)
+- volume_spike: Trading volume increases X% (requires: token, threshold)
 - price_level: Price crosses above/below X (requires: token, price, direction)
 
 Output ONLY valid JSON with this schema:
@@ -71,18 +71,17 @@ Output ONLY valid JSON with this schema:
     "conditions": [
         {
             "type": "price_drop|price_rise|volume_spike|price_level",
-            "params": {
             "token": "TOKEN_SYMBOL",
-                "threshold_percent": number,  // for price_drop, price_rise, volume_spike
+            "chain": "bsc",
+            "threshold": number,  // for price_drop, price_rise, volume_spike
             "price": number,     // for price_level
-                "direction": "above|below"    // for price_level
-            }
+            "direction": "above|below",  // for price_level
+            "timeframe": "1h"
         }
     ],
     "actions": [
         {
-            "type": "buy|sell|notify",
-            "params": {}
+            "type": "buy|sell|notify"
         }
     ]
 }