feat(server/db): 数据层多库支持(1/4)— 连接分派 + 双方言迁移管线

- config 增 DB_DRIVER(mysql 默认 | sqlite);DSN 对 sqlite 为文件路径
- db.OpenDriver 按驱动分派:sqlite 用 modernc(纯 Go 免 CGO)+ WAL/
  busy_timeout/foreign_keys/_txlock=immediate;mysql 路径不变
- store.Open 分派;mysql 保留 UTC/collation 断言,sqlite 跳过
- 迁移拆 migrations/{mysql,sqlite}/ 双套,embed 双 FS,migrate 按驱动选源
  与 golang-migrate 驱动;修复 m.Close() 误关调用方 *sql.DB 的坑
- cmd/migrate 串入 DB_DRIVER;集成测试 MigrateUp 签名更新
- 新增 SQLite 时间往返 smoke 测试与端到端迁移测试(免 docker)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/internal/store/sqlite_migrate_test.go

@@ -0,0 +1,93 @@
+package store_test
+
+import (
+	"testing"
+
+	"github.com/wangjia/pangolin/server/internal/config"
+	"github.com/wangjia/pangolin/server/internal/store"
+)
+
+// TestSQLiteMigrateUpDown verifies the SQLite migration set applies cleanly,
+// is idempotent, seeds correctly, and rolls back — no container required, so it
+// runs in normal CI (unlike the MySQL integration test behind //go:build integration).
+func TestSQLiteMigrateUpDown(t *testing.T) {
+	cfg := &config.Config{Driver: "sqlite", DSN: ":memory:"}
+	db, err := store.Open(cfg)
+	if err != nil {
+		t.Fatalf("store.Open(sqlite): %v", err)
+	}
+	defer db.Close()
+
+	// 1. MigrateUp.
+	if err := store.MigrateUp(db, "sqlite"); err != nil {
+		t.Fatalf("MigrateUp: %v", err)
+	}
+	v, dirty, err := store.MigrateVersion(db, "sqlite")
+	if err != nil {
+		t.Fatalf("MigrateVersion: %v", err)
+	}
+	if dirty {
+		t.Fatalf("schema dirty after MigrateUp")
+	}
+	if v != 13 {
+		t.Errorf("version = %d, want 13", v)
+	}
+
+	// 2. Core tables exist.
+	for _, tbl := range []string{
+		"users", "devices", "plans", "subscriptions", "code_batches", "codes",
+		"usage_daily", "audit_log", "providers", "nodes", "node_events",
+		"directory_version", "provision_idempotency", "replacements", "admins",
+		"connect_credentials",
+	} {
+		var name string
+		err := db.QueryRow(
+			`SELECT name FROM sqlite_master WHERE type='table' AND name=?`, tbl,
+		).Scan(&name)
+		if err != nil {
+			t.Errorf("table %q missing: %v", tbl, err)
+		}
+	}
+
+	// 3. Seed: 3 plans + directory_version singleton.
+	var plans int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM plans`).Scan(&plans); err != nil {
+		t.Fatalf("count plans: %v", err)
+	}
+	if plans != 3 {
+		t.Errorf("plans seeded = %d, want 3", plans)
+	}
+	var dv int
+	if err := db.QueryRow(`SELECT version FROM directory_version WHERE id=1`).Scan(&dv); err != nil {
+		t.Errorf("directory_version singleton missing: %v", err)
+	}
+
+	// 4. Added columns from later migrations are present (000011 / 000013).
+	if _, err := db.Exec(`SELECT reality_prk, reality_short_id, sub_token, totp_enabled FROM nodes
+		LEFT JOIN users ON 0=1 LIMIT 0`); err != nil {
+		// Separate queries — the join above is just a cheap column-existence probe.
+		if _, e := db.Exec(`SELECT reality_prk, reality_short_id FROM nodes LIMIT 0`); e != nil {
+			t.Errorf("nodes reality cols missing: %v", e)
+		}
+		if _, e := db.Exec(`SELECT sub_token, totp_secret_enc, totp_enabled FROM users LIMIT 0`); e != nil {
+			t.Errorf("users totp cols missing: %v", e)
+		}
+	}
+
+	// 5. Idempotent second MigrateUp.
+	if err := store.MigrateUp(db, "sqlite"); err != nil {
+		t.Fatalf("MigrateUp (idempotent): %v", err)
+	}
+
+	// 6. MigrateDown returns to baseline.
+	if err := store.MigrateDown(db, "sqlite"); err != nil {
+		t.Fatalf("MigrateDown: %v", err)
+	}
+	v2, _, err := store.MigrateVersion(db, "sqlite")
+	if err != nil {
+		t.Fatalf("MigrateVersion after down: %v", err)
+	}
+	if v2 != 0 {
+		t.Errorf("version after down = %d, want 0", v2)
+	}
+}