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

migrate_sqlite_to_pg.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+"""
+SQLite to PostgreSQL Migration Script
+
+Reads candle data from a SQLite database and writes it to PostgreSQL.
+This is a one-time migration tool used to transfer existing historical
+data from the old SQLite database to the new PostgreSQL database.
+
+Usage:
+    python migrate_sqlite_to_pg.py --sqlite-path _data/market_data.db --log-level normal
+
+The script:
+1. Connects to both SQLite (source) and PostgreSQL (destination)
+2. Enumerates all candle tables (skipping legacy tables like market_cap)
+3. For each table, reads data from SQLite and upserts to PostgreSQL
+4. Handles table name sanitization (colons → underscores)
+"""
+
+import argparse
+import logging
+import os
+import sqlite3
+import sys
+
+import pandas as pd
+
+from logging_utils import setup_logging
+from db import get_connection, sanitize_table_name, upsert_candles, create_candle_table
+
+TIMEFRAMES = [
+    '1m', '3m', '5m', '15m', '30m', '37m', '148m',
+    '1h', '2h', '4h', '8h', '12h', '1d', '3d', '1w', '1month'
+]
+
+
+def get_candle_tables(sqlite_conn):
+    """Get all candle table names from SQLite (excluding legacy tables)."""
+    cursor = sqlite_conn.cursor()
+    cursor.execute("SELECT name FROM sqlite_master WHERE type='table'")
+    all_tables = [row[0] for row in cursor.fetchall()]
+
+    candle_tables = []
+    for table in all_tables:
+        for tf in TIMEFRAMES:
+            if table.endswith(f'_{tf}'):
+                candle_tables.append(table)
+                break
+
+    return candle_tables
+
+
+def parse_table_name(table_name):
+    """Parse a table name into (coin, timeframe)."""
+    for tf in TIMEFRAMES:
+        suffix = f'_{tf}'
+        if table_name.endswith(suffix):
+            coin = table_name[:-len(suffix)]
+            return coin, tf
+    return table_name, '1m'
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Migrate data from SQLite to PostgreSQL.")
+    parser.add_argument("--sqlite-path", default="_data/market_data.db",
+                        help="Path to the SQLite database file.")
+    parser.add_argument("--log-level", default="normal", choices=['off', 'normal', 'debug'])
+    args = parser.parse_args()
+
+    setup_logging(args.log_level, 'Migrator')
+
+    if not os.path.exists(args.sqlite_path):
+        logging.error(f"SQLite database not found at '{args.sqlite_path}'")
+        sys.exit(1)
+
+    sqlite_conn = sqlite3.connect(args.sqlite_path)
+    pg_conn = get_connection()
+
+    tables = get_candle_tables(sqlite_conn)
+    logging.info(f"Found {len(tables)} candle tables to migrate")
+
+    for table_name in tables:
+        coin, timeframe = parse_table_name(table_name)
+        pg_table = sanitize_table_name(coin, timeframe)
+
+        logging.info(f"Migrating {table_name} -> {pg_table}")
+
+        df = pd.read_sql(f'SELECT * FROM "{table_name}"', sqlite_conn)
+        if df.empty:
+            logging.warning(f"Table {table_name} is empty, skipping")
+            continue
+
+        create_candle_table(pg_conn, pg_table)
+
+        records = list(df.itertuples(index=False, name=None))
+        upsert_candles(pg_conn, pg_table, records)
+
+        logging.info(f"Migrated {len(records)} rows to {pg_table}")
+
+    sqlite_conn.close()
+    pg_conn.close()
+    logging.info("Migration complete!")
+
+
+if __name__ == "__main__":
+    main()