feat: productionize local service — fix signal pipeline, lower thresholds, add company-name ticker extraction

- Point Ollama to local instance via host.docker.internal, use gemma3 model
- Remove Docker Ollama service (using host's Ollama instead)
- Add company-name-to-ticker mapping (Apple→AAPL, Tesla→TSLA, etc.) for RSS articles
- Lower signal thresholds for faster feedback with paper trading:
  - FinBERT confidence: 0.6→0.4, signal strength: 0.3→0.15
  - News strategy: article_count 2→1, confidence 0.5→0.3, score ±0.3→±0.15
- Fix market data BarSet access bug (BarSet.__contains__ returns False incorrectly)
- Fix market data SIP feed error by switching to IEX feed for free Alpaca accounts
- Fix nginx proxy routing for /api/auth/* to api-gateway /auth/*
- Add seed_sample_data script
- Update tests for new thresholds and alpaca mock modules

services/signal_generator/config.py

@@ -8,7 +8,7 @@ class SignalGeneratorConfig(BaseConfig):
 
     alpaca_api_key: str = ""
     alpaca_secret_key: str = ""
-    signal_strength_threshold: float = 0.3
+    signal_strength_threshold: float = 0.15
     watchlist: list[str] = []
 
     model_config = {"env_prefix": "TRADING_"}