Migrate data pipeline from SQLite to PostgreSQL + Docker setup

- Add db.py PostgreSQL abstraction layer (connection, upsert, table mgmt)
- Replace sqlite3 with psycopg2 in: live_candle_fetcher, resampler,
  data_fetcher, fetch_history, import_csv, indicators, base_strategy
- Sanitize table names (colons -> underscores) for PostgreSQL compat
- Replace INSERT OR REPLACE with ON CONFLICT upserts
- Replace pandas to_sql() with batch upsert_candles()
- Add scripts: resampler_loop, gap_detector, backup_runner, cron_scheduler
- Add migrate_sqlite_to_pg.py for one-time data migration
- Add Dockerfile, docker-compose.yml, supervisord.conf
- Add postgres/postgresql.conf tuned for 4GB RAM (Synology DS1513+)
- Add .dockerignore, .env.docker.example, secrets template
- Update requirements.txt (psycopg2-binary), .gitignore
- Add MIGRATION_PLAN.md with full plan and todo list

indicators_fetcher.py

@@ -29,7 +29,7 @@ class IndicatorsFetcher:
         setup_logging(log_level, 'IndicatorsFetcher')
 
         project_root = os.path.dirname(os.path.abspath(__file__))
-        self.db_path = os.path.join(project_root, "_data", "market_data.db")
+        self.db_path = os.environ.get("PG_CONN_STR", "postgresql://hyper:hyper@localhost:5432/hyper")
         self.config_path = os.path.join(project_root, "_data", "indicators.json")
         self.status_file_path = os.path.join(project_root, "_logs", "indicators_status.json")