T17: backend penyimpanan bersama db.py (sqlite | mysql via PyMySQL)

- db.py: abstraksi connect/query/queryone/replace_snapshot; %s → ? utk sqlite;
  replace snapshot mysql = CREATE IF NOT EXISTS + DELETE + INSERT (MVCC)
- config/.env.example: VEX_DB_BACKEND (default sqlite) + VEX_DB_HOST/PORT/USER/PASS/NAME
- get_voters.persist → db.replace_snapshot; dashboard baca via db.query
- LIKE pakai ESCAPE '!' (backslash memutus literal string MySQL, B2);
  db.query selalu kembalikan list (PyMySQL tuple vs sqlite list, B3)
- docker-compose.yml: kontainer uji mariadb:11 (databisnisid-mariadb, 127.0.0.1:3306)
- test_mariadb.py: suite integrasi opt-in (skip bila bukan mysql)
- SPEC.md §V17/T17/B2/B3; AGENTS.md runbook

get_voters.py

@@ -5,14 +5,14 @@ dibuang. Berjalan imparsial (repeatable) dan siap dijadwalkan (cron).
 """
 
 import math
-import sqlite3
 import sys
 import time
 from datetime import datetime, timedelta, timezone
 
 import requests
 
-from config import API_NODE, DB_PATH, MIN_STAKED_VEX, TARGET_BP, VEX_STALE_DAYS
+import db
+from config import API_NODE, MIN_STAKED_VEX, TARGET_BP, VEX_STALE_DAYS
 
 # Kontrak & scope sistem Vexanium = vexcore (BUKAN vexio sesuai konvensi EOS)
 CODE = 'vexcore'
@@ -145,33 +145,14 @@ def normalize(row, now=None):
 
 
 def persist(rows):
-    """V7: ganti snapshot — DROP+INSERT tiap skan, ⊥ history/append.
+    """V7: ganti snapshot — tiap skan ⊥ history/append.
 
-    WAL: journal_mode=WAL → pembaca (dashboard multi-worker) tak terblokir
-    saat DROP+INSERT harian. Mode ini persisten setelah diset.
+    Delegasi ke `db.replace_snapshot` (backend sqlite/mysql):
+    sqlite DROP+CREATE dalam WAL → pembaca (dashboard multi-worker) tak
+    terblokir; mysql DELETE+INSERT dalam satu transaksi (MVCC snapshot).
     """
     scanned_at = datetime.now().isoformat(timespec='seconds')
-    conn = sqlite3.connect(DB_PATH)
-    try:
-        conn.execute('PRAGMA journal_mode=WAL')
-        conn.execute('DROP TABLE IF EXISTS voters')  # snapshot bersih
-        conn.execute(
-            'CREATE TABLE voters ('  # I.db
-            'owner TEXT PRIMARY KEY, '
-            'weight TEXT NOT NULL, '
-            'staked REAL NOT NULL, '
-            'scanned_at TEXT NOT NULL, '
-            'last_vote TEXT)'
-        )
-        conn.executemany(
-            'INSERT INTO voters (owner, weight, staked, scanned_at, last_vote) '
-            'VALUES (?, ?, ?, ?, ?)',
-            [(r['owner'], r['weight'], r['staked'], scanned_at, r.get('last_vote'))
-             for r in rows],
-        )
-        conn.commit()
-    finally:
-        conn.close()
+    db.replace_snapshot(rows, scanned_at)
     return scanned_at