Add Android control app and embedded server

Inspired by HNKServer/honoka-chan-apk-server, but implemented as a JNI-based embedded runtime instead of the original approach.

- Add an Android Compose controller app that starts and stops honoka-chan through JNI, shows runtime and health status, manages data directory mounting, and supports backup import/export for data.db
- Add an embeddable Go server entrypoint plus JNI-exported status, health, and reload hooks so desktop and Android builds share the same startup and shutdown path
- Add Android build scripts, runtime packaging, and project documentation, including generated default config.json content for honoka_runtime.zip
- Add runtime bundle hash tracking so updated honoka_runtime.zip assets are automatically redeployed while preserving config.json and user data files
- Add in-app service settings for unlock_all_special_rotation with immediate config persistence and automatic reload when the service is running
- Split SQLite driver selection by platform, using go-sqlite3 on Android and modernc.org/sqlite elsewhere to avoid Android x86_64 seccomp crashes
- Update startup, database initialization, and system health/reload handlers to support the embedded runtime and Android control flow

Signed-off-by: Sean Du <do4suki@gmail.com>

internal/handler/system/system.go

@@ -0,0 +1,139 @@
+package system
+
+import (
+	"encoding/json"
+	"errors"
+	"honoka-chan/config"
+	"honoka-chan/internal/router"
+	systemschema "honoka-chan/internal/schema/system"
+	"honoka-chan/pkg/db"
+	"net/http"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+var (
+	startedAt    = time.Now()
+	lastReloadAt atomic.Int64
+)
+
+const dateTimeFormat = "2006-01-02 15:04:05"
+
+func MarkStarted(t time.Time) {
+	startedAt = t
+}
+
+func Health() (systemschema.HealthResp, int) {
+	appName := config.Conf.AppName
+	if appName == "" {
+		appName = "honoka-chan"
+	}
+
+	mainDBStatus := "not initialized"
+	if db.MainEng != nil {
+		mainDBStatus = "ok"
+		if err := db.MainEng.Ping(); err != nil {
+			mainDBStatus = err.Error()
+		}
+	}
+
+	userDBStatus := "not initialized"
+	if db.UserEng != nil {
+		userDBStatus = "ok"
+		if err := db.UserEng.Ping(); err != nil {
+			userDBStatus = err.Error()
+		}
+	}
+
+	status := "ok"
+	statusCode := http.StatusOK
+	if db.MainEng == nil || db.UserEng == nil {
+		status = "stopped"
+	}
+
+	resp := systemschema.HealthResp{
+		Status:                status,
+		AppName:               appName,
+		Version:               config.PackageVersion,
+		StartedAt:             startedAt.Format(dateTimeFormat),
+		UptimeSeconds:         int64(time.Since(startedAt).Seconds()),
+		ListenPort:            config.Conf.Settings.ListenPort,
+		CdnServer:             config.Conf.Settings.CdnServer,
+		ReloadTokenConfigured: strings.TrimSpace(config.Conf.Settings.ReloadToken) != "",
+		MainDB:                mainDBStatus,
+		UserDB:                userDBStatus,
+	}
+
+	if ts := lastReloadAt.Load(); ts > 0 {
+		resp.LastReloadAt = time.Unix(ts, 0).Format(dateTimeFormat)
+	}
+
+	if status == "ok" && (mainDBStatus != "ok" || userDBStatus != "ok") {
+		resp.Status = "degraded"
+		statusCode = http.StatusServiceUnavailable
+	}
+
+	return resp, statusCode
+}
+
+func HealthJSON() string {
+	resp, _ := Health()
+	data, err := json.Marshal(resp)
+	if err != nil {
+		return `{"status":"error","app_name":"honoka-chan"}`
+	}
+	return string(data)
+}
+
+func Reload(token string, requireToken bool) (systemschema.ReloadResp, int, error) {
+	expectedToken := strings.TrimSpace(config.Conf.Settings.ReloadToken)
+	if requireToken && expectedToken == "" {
+		return systemschema.ReloadResp{
+			Status:  "error",
+			Message: "reload_token is not configured",
+		}, http.StatusServiceUnavailable, errors.New("reload_token is not configured")
+	}
+
+	if requireToken && strings.TrimSpace(token) != expectedToken {
+		return systemschema.ReloadResp{
+			Status:  "error",
+			Message: "invalid reload token",
+		}, http.StatusUnauthorized, errors.New("invalid reload token")
+	}
+
+	config.ReloadConfig()
+	now := time.Now()
+	lastReloadAt.Store(now.Unix())
+
+	return systemschema.ReloadResp{
+		Status:     "ok",
+		Message:    "configuration reloaded",
+		ReloadedAt: now.Format(dateTimeFormat),
+	}, http.StatusOK, nil
+}
+
+func health(ctx *gin.Context) {
+	resp, statusCode := Health()
+	ctx.JSON(statusCode, resp)
+}
+
+func reload(ctx *gin.Context) {
+	token := strings.TrimSpace(ctx.GetHeader("X-Reload-Token"))
+	if token == "" {
+		token = strings.TrimSpace(ctx.Query("token"))
+	}
+	if token == "" {
+		token = strings.TrimSpace(ctx.PostForm("token"))
+	}
+
+	resp, statusCode, _ := Reload(token, true)
+	ctx.JSON(statusCode, resp)
+}
+
+func init() {
+	router.AddHandler("/", "GET", "/system/health", health)
+	router.AddHandler("/", "POST", "/system/reload", reload)
+}