Add global role synchronization for Discord with configurable interval

This commit introduces a new feature for global role synchronization in Discord, allowing for periodic reconciliation of managed roles. A new environment variable, `DISCORD_GLOBAL_SYNC_INTERVAL`, has been added to configure the synchronization interval, defaulting to 5 minutes. The `RoleWorker` has been updated to schedule global sync jobs, ensuring that missing managed roles are restored and extra assignments are removed without affecting unrelated server roles. Database schema changes support the new synchronization logic, and tests have been added to validate the functionality of the global reconciliation process.

backend/cmd/api/main.go

@@ -59,9 +59,10 @@ func main() {
 	discordGuildID := os.Getenv("DISCORD_GUILD_ID")
 	if discordGuildID != "" {
 		roleWorker, roleErr := discordadapter.NewRoleWorker(store, discordadapter.RoleSyncConfig{
-			BotToken: discordBotToken,
-			GuildID:  discordGuildID,
-			Locale:   env("DISCORD_ANNOUNCEMENT_LOCALE", "ru"),
+			BotToken:           discordBotToken,
+			GuildID:            discordGuildID,
+			Locale:             env("DISCORD_ANNOUNCEMENT_LOCALE", "ru"),
+			GlobalSyncInterval: durationEnv("DISCORD_GLOBAL_SYNC_INTERVAL", 5*time.Minute),
 		})
 		if roleErr != nil {
 			slog.Error("Discord role sync configuration failed", "error", roleErr)