feat: add SQLite support, setup wizard enhancements, and live dashboard

Add zero-dependency SQLite mode so users can run Erupe without
PostgreSQL. A transparent db.DB wrapper auto-translates PostgreSQL
SQL ($N placeholders, now(), ::casts, ILIKE, public. prefix,
TRUNCATE) for SQLite at runtime — all 28 repo files use the wrapper
with no per-query changes needed.

Setup wizard gains two new steps: quest file detection with download
link, and gameplay presets (solo/small/community/rebalanced). The API
server gets a /dashboard endpoint with auto-refreshing stats.

CI release workflow now builds and pushes Docker images to GHCR
alongside binary artifacts on tag push.

Key changes:
- common/db: DB/Tx wrapper with 6 SQL translation rules
- server/migrations/sqlite: full SQLite schema (0001-0005)
- config: Database.Driver field ("postgres" or "sqlite")
- main.go: SQLite connection with WAL mode, single writer
- server/setup: quest check + preset selection steps
- server/api: /dashboard with live stats
- .github/workflows: Docker in release, deduplicate docker.yml

server/channelserver/repo_mail_test.go

@@ -1,6 +1,7 @@
 package channelserver
 
 import (
+	dbutil "erupe-ce/common/db"
 	"testing"
 
 	"github.com/jmoiron/sqlx"
@@ -13,7 +14,7 @@ func setupMailRepo(t *testing.T) (*MailRepository, *sqlx.DB, uint32, uint32) {
 	senderID := CreateTestCharacter(t, db, userID, "Sender")
 	userID2 := CreateTestUser(t, db, "mail_recipient")
 	recipientID := CreateTestCharacter(t, db, userID2, "Recipient")
-	repo := NewMailRepository(db)
+	repo := NewMailRepository(dbutil.Wrap(db))
 	t.Cleanup(func() { TeardownTestDB(t, db) })
 	return repo, db, senderID, recipientID
 }