refactor: remove mock trading functionality from backend and frontend

Removes all mock price simulation features:
- Delete MockPriceManager from backend/data/
- Remove mock_mode, enable_mock, is_mock_mode flags from services
- Remove mock CLI options and config
- Remove mock mode UI components and state from frontend
- Update tests to remove mock references

Now system supports only live and backtest modes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/core/pipeline_runner.py

@@ -244,10 +244,8 @@ async def run_pipeline(
         start_date = bootstrap.get("start_date")
         end_date = bootstrap.get("end_date")
         enable_memory = bootstrap.get("enable_memory", False)
-        enable_mock = bootstrap.get("enable_mock", False)
 
         is_backtest = mode == "backtest"
-        is_mock = enable_mock or mode == "mock" or (not is_backtest and os.getenv("MOCK_MODE", "false").lower() == "true")
 
         # ======================================================================
         # PHASE 0: Initialize runtime manager
@@ -288,9 +286,8 @@ async def run_pipeline(
         market_service = MarketService(
             tickers=tickers,
             poll_interval=10,
-            mock_mode=is_mock and not is_backtest,
             backtest_mode=is_backtest,
-            api_key=os.getenv("FINNHUB_API_KEY") if not is_mock and not is_backtest else None,
+            api_key=os.getenv("FINNHUB_API_KEY") if not is_backtest else None,
             backtest_start_date=start_date if is_backtest else None,
             backtest_end_date=end_date if is_backtest else None,
         )
@@ -387,7 +384,6 @@ async def run_pipeline(
             scheduler_callback=scheduler_callback,
             config={
                 "mode": mode,
-                "mock_mode": is_mock,
                 "backtest_mode": is_backtest,
                 "tickers": tickers,
                 "config_name": run_id,