feat(ui): 接入 vendor 真实图标库 + 图标选择器

- assets/icons/ 共 80+ 张真实品牌图标嵌入 UI 包
- entry 新增 IconKey 字段，持久化到 config.Entry.IconName
- iconPickerDialog 网格布局图标选择器
- Add 完成后自动弹出图标选择器，Skip 则用 vendor 占位图
- ⋯ 菜单新增 "Change icon..." 项
- vendorIconFor 解析顺序：catalog → vendor 占位 → qr 兜底

internal/ui/vendor_icons.go

@@ -5,20 +5,88 @@ import (
 	"embed"
 	"image"
 	_ "image/png"
+	"sort"
+	"strings"
+	"sync"
 
 	"git.wxccs.org/iceking2nd/winauth-go/internal/global"
 )
 
-//go:embed assets/vendor_icons/*.png assets/app_icon.png
+//go:embed assets/vendor_icons/*.png assets/icons/*.png assets/app_icon.png
 var assetsFS embed.FS
 
+var (
+	// iconCatalog holds all decoded brand-icons keyed by stem (filename
+	// without ".png"). Populated once on first access.
+	iconCatalog     map[string]image.Image
+	iconCatalogOnce sync.Once
+	iconSortedKeys  []string
+)
+
+// loadIconCatalog decodes every PNG from assets/icons/ into iconCatalog.
+// Also populates iconSortedKeys for the icon picker.
+func loadIconCatalog() {
+	const fn = "internal.ui.loadIconCatalog"
+	iconCatalog = map[string]image.Image{}
+
+	dir, err := assetsFS.ReadDir("assets/icons")
+	if err != nil {
+		global.Log.WithField("func", fn).WithError(err).Warn("read icons dir failed")
+		return
+	}
+
+	var keys []string
+	for _, entry := range dir {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".png") {
+			continue
+		}
+		key := strings.TrimSuffix(entry.Name(), ".png")
+		data, err := assetsFS.ReadFile("assets/icons/" + entry.Name())
+		if err != nil {
+			continue
+		}
+		img, _, err := image.Decode(bytes.NewReader(data))
+		if err != nil {
+			global.Log.WithField("func", fn).WithError(err).
+				WithField("file", entry.Name()).Warn("icon decode failed")
+			continue
+		}
+		iconCatalog[key] = img
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	iconSortedKeys = keys
+	global.Log.WithField("func", fn).WithField("count", len(keys)).Debug("icons loaded")
+}
+
+// allIconKeys returns the sorted list of available icon keys for the
+// icon picker. Safe to call before icons are loaded — triggers load.
+func allIconKeys() []string {
+	iconCatalogOnce.Do(loadIconCatalog)
+	return iconSortedKeys
+}
+
+// iconByKey returns the named icon or nil. Safe to call before icons are
+// loaded — triggers load.
+func iconByKey(key string) image.Image {
+	iconCatalogOnce.Do(loadIconCatalog)
+	return iconCatalog[key]
+}
+
+// ---------------------------------------------------------------------------
+// Original vendor-icon fallbacks (assets/vendor_icons/). These are simple
+// placeholder squares with a single initial — kept so old entries without an
+// IconKey still render something recognisable.
+
 // vendorIcons holds the decoded vendor PNGs keyed by the authenticator
-// Name() return value. Built once at first lookup so we pay the decode
-// cost once per process instead of per frame.
+// Name() return value. Built once at first lookup.
 var vendorIcons = map[string]image.Image{}
 
-func loadVendorIcons() {
-	const fn = "internal.ui.loadVendorIcons"
+func ensureVendorIcons() {
+	const fn = "internal.ui.ensureVendorIcons"
+	if len(vendorIcons) > 0 {
+		return
+	}
 	files := []string{"google", "microsoft", "okta", "hotp", "battlenet", "steam", "qr"}
 	for _, name := range files {
 		data, err := assetsFS.ReadFile("assets/vendor_icons/" + name + ".png")
@@ -37,24 +105,28 @@ func loadVendorIcons() {
 	}
 }
 
-// vendorIconFor returns the icon image bound to the given authenticator
-// vendor key ("google", "microsoft", ...). Falls back to the generic
-// "qr" tile when no specific icon is registered, and nil when even that
-// is unavailable (only happens if the embed is broken).
-func vendorIconFor(vendor string) image.Image {
-	if len(vendorIcons) == 0 {
-		loadVendorIcons()
+// vendorIconFor returns the icon image for the given key. Resolution
+// order:
+//  1. iconCatalog (full brand icons from assets/icons/)
+//  2. vendorIcons (fallback placeholders from assets/vendor_icons/)
+//  3. vendorIcons["qr"] (generic fallback)
+//
+// This preserves backward compatibility: callers that pass a vendor name
+// ("google", "steam", …) still get their placeholder.
+func vendorIconFor(key string) image.Image {
+	iconCatalogOnce.Do(loadIconCatalog)
+	ensureVendorIcons()
+	if img, ok := iconCatalog[key]; ok {
+		return img
 	}
-	if img, ok := vendorIcons[vendor]; ok {
+	if img, ok := vendorIcons[key]; ok {
 		return img
 	}
 	return vendorIcons["qr"]
 }
 
 // AppIcon returns the decoded application icon, or nil if the asset is
-// missing. Currently unused at runtime — Gio v0.7 has no API to set a
-// window icon, so this exists so callers (e.g. a future tray bucket)
-// can reuse the same bitmap.
+// missing.
 func AppIcon() image.Image {
 	data, err := assetsFS.ReadFile("assets/app_icon.png")
 	if err != nil {