Add project setup: dependencies, config, and package scaffolding

- requirements.txt with all core dependencies (streamlit, binance, ta, anthropic, praw, etc.)
- .env.example template for all required API keys
- .gitignore covering secrets, caches, db files, and logs
- config.py loading env vars with trading defaults and signal weights
- tests/conftest.py with sys.path fix for imports
- Empty __init__.py files for tests, data, agents, engine, dashboard, scheduler packages

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

.env.example

@@ -0,0 +1,9 @@
+BINANCE_API_KEY=
+BINANCE_SECRET=
+CRYPTOPANIC_API_KEY=
+NEWS_API_KEY=
+TWITTER_BEARER_TOKEN=
+REDDIT_CLIENT_ID=
+REDDIT_SECRET=
+REDDIT_USER_AGENT=crypto_signal_bot/1.0
+ANTHROPIC_API_KEY=