feat: add admin panel with multi-chain support and notification system

- Add full admin REST API: auth, API keys, chains, chain tokens, wallets,
  orders, RPC nodes, settings, dashboard stats, notifications
- Add JWT-based admin authentication and API key auth middleware
- Add multi-chain listeners: BSC, ETH, Polygon, Plasma, EVM WebSocket
- Add RPC node health check job with automatic failover
- Add Telegram notification channel for order events
- Add installer for first-run database initialization
- Add new DB models: admin_user, api_key, chain, chain_token,
  rpc_node, settings, notification_channel
- Add order statistics aggregation (daily/monthly/by-chain)
- Serve built admin SPA from embedded www/ assets
- Add comprehensive test coverage for all new features

src/config/config.go

@@ -7,6 +7,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
@@ -15,6 +16,12 @@ import (
 	"github.com/tidwall/gjson"
 )
 
+// parseFloat is the minimal helper used by the settings bridge; kept
+// here so settings_bridge.go stays import-free.
+func parseFloat(s string) (float64, error) {
+	return strconv.ParseFloat(strings.TrimSpace(s), 64)
+}
+
 var (
 	HTTPAccessLog      bool
 	SQLDebug           bool
@@ -124,6 +131,57 @@ func resolveConfigFilePath() (string, error) {
 	return normalizeConfiguredPath(".env")
 }
 
+// NeedsInstall returns true when the first-run install wizard should run.
+// It returns true if the config file does not exist yet, or if the file
+// exists and contains install=true (an explicit reset flag).
+// Existing installs that have no install key are NOT affected.
+func NeedsInstall() bool {
+	envPath, exists := ResolveConfigPath()
+	if !exists {
+		return true
+	}
+	// Read just the install key without triggering full Init().
+	v := viper.New()
+	v.SetConfigFile(envPath)
+	if err := v.ReadInConfig(); err != nil {
+		// Unreadable config → treat as needing install.
+		return true
+	}
+	return strings.EqualFold(strings.TrimSpace(v.GetString("install")), "true")
+}
+
+// ResolveConfigPath returns the absolute path to the .env file and whether
+// it currently exists on disk. Unlike resolveConfigFilePath it does not
+// return an error when the file is absent — callers (e.g. the install
+// wizard) need the target path even before the file is written.
+func ResolveConfigPath() (path string, exists bool) {
+	candidate := explicitConfigPath
+	if candidate == "" {
+		if e := strings.TrimSpace(os.Getenv("EPUSDT_CONFIG")); e != "" {
+			candidate = e
+		} else {
+			candidate = ".env"
+		}
+	}
+	// Resolve relative paths against cwd.
+	p := strings.TrimSpace(candidate)
+	if !filepath.IsAbs(p) {
+		cwd, err := os.Getwd()
+		if err == nil {
+			p = filepath.Join(cwd, p)
+		}
+	}
+	info, err := os.Stat(p)
+	if err == nil && info.IsDir() {
+		p = filepath.Join(p, ".env")
+		info, err = os.Stat(p)
+	}
+	if err != nil {
+		return p, false
+	}
+	return p, true
+}
+
 func normalizeConfiguredPath(input string) (string, error) {
 	path := strings.TrimSpace(input)
 	if path == "" {
@@ -178,11 +236,19 @@ func GetAppUri() string {
 	return viper.GetString("app_uri")
 }
 
-func GetApiAuthToken() string {
-	return viper.GetString("api_auth_token")
+func GetRateApiUrl() string {
+	// settings table wins (admin-configurable); .env and env var remain
+	// as fallbacks for smooth migration from the old layout.
+	if db := settingsRateApiUrl(); db != "" {
+		return db
+	}
+	return GetRateApiUrlFromEnv()
 }
 
-func GetRateApiUrl() string {
+// GetRateApiUrlFromEnv returns the rate API URL read only from the
+// .env / environment variables, bypassing the settings table. Used
+// by bootstrap to seed the settings table from the initial .env value.
+func GetRateApiUrlFromEnv() string {
 	rateURL := viper.GetString("api_rate_url")
 	if rateURL == "" {
 		rateURL = os.Getenv("API_RATE_URL")
@@ -190,7 +256,6 @@ func GetRateApiUrl() string {
 	if rateURL == "" {
 		log.Println("api_rate_url is empty")
 	}
-	RateApiUrl = rateURL
 	return rateURL
 }
 
@@ -250,6 +315,11 @@ func GetRateForCoin(coin string, base string) float64 {
 }
 
 func GetUsdtRate() float64 {
+	// Prefer the DB-backed override (admin-configurable). Fall back to
+	// the legacy .env var, then the hardcoded 6.4 default.
+	if forced := settingsForcedUsdtRate(); forced > 0 {
+		return forced
+	}
 	forcedUsdtRate := viper.GetFloat64("forced_usdt_rate")
 	if forcedUsdtRate > 0 {
 		return forcedUsdtRate
@@ -340,11 +410,3 @@ func GetSolanaRpcUrl() string {
 func GetEthereumWsUrl() string {
 	return strings.TrimSpace(viper.GetString("ethereum_ws_url"))
 }
-
-func GetEpayPid() int {
-	return viper.GetInt("epay_pid")
-}
-
-func GetEpayKey() string {
-	return viper.GetString("epay_key")
-}

src/config/settings_bridge.go

@@ -0,0 +1,34 @@
+package config
+
+// Settings lookups are injected at runtime by bootstrap (after DB init)
+// to keep the config package free of a `model/data` import, which would
+// create a cycle via `model/dao -> config`.
+//
+// If unset (e.g. during early startup or tests) the getters return the
+// zero string / 0 and callers fall through to the .env / default path.
+
+// SettingsGetString is installed by bootstrap.Init with a closure that
+// reads from the settings table. Runtime-only.
+var SettingsGetString func(key string) string
+
+func settingsRateApiUrl() string {
+	if SettingsGetString == nil {
+		return ""
+	}
+	return SettingsGetString("rate.api_url")
+}
+
+func settingsForcedUsdtRate() float64 {
+	if SettingsGetString == nil {
+		return 0
+	}
+	raw := SettingsGetString("rate.forced_usdt_rate")
+	if raw == "" {
+		return 0
+	}
+	f, err := parseFloat(raw)
+	if err != nil {
+		return 0
+	}
+	return f
+}