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/setup/handlers.go

@@ -45,6 +45,15 @@ func (ws *wizardServer) handleClientModes(w http.ResponseWriter, _ *http.Request
 	writeJSON(w, http.StatusOK, map[string]interface{}{"modes": clientModes()})
 }
 
+func (ws *wizardServer) handleCheckQuests(w http.ResponseWriter, _ *http.Request) {
+	status := checkQuestFiles("")
+	writeJSON(w, http.StatusOK, status)
+}
+
+func (ws *wizardServer) handlePresets(w http.ResponseWriter, _ *http.Request) {
+	writeJSON(w, http.StatusOK, map[string]interface{}{"presets": availablePresets()})
+}
+
 // testDBRequest is the JSON body for POST /api/setup/test-db.
 type testDBRequest struct {
 	Host     string `json:"host"`