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/app.go

@@ -56,6 +56,11 @@ type entry struct {
 	Auth authenticator.Authenticator
 	Code string
 
+	// IconKey selects a specific brand icon from the embedded catalog
+	// (e.g. "GitHubIcon", "DropboxIcon"). Empty means fall back to the
+	// vendor-name placeholder ("google", "steam", …).
+	IconKey string
+
 	// Hotkey is the user-configured global shortcut string ("Ctrl+Alt+G")
 	// or "" if none is set.
 	Hotkey string
@@ -106,6 +111,7 @@ type appState struct {
 	rowMenu       *rowActionMenu
 	renameDlg     *renameDialog
 	confirmDelDlg *confirmDeleteDialog
+	iconPickerDlg *iconPickerDialog
 	rowTargetIdx  int
 
 	store   *store
@@ -144,7 +150,7 @@ func (st *appState) snapshotEntries() []config.Entry {
 	defer st.mu.Unlock()
 	out := make([]config.Entry, 0, len(st.entries))
 	for _, en := range st.entries {
-		out = append(out, entryFromAuthenticator(en.Name, en.Auth, en.Hotkey))
+		out = append(out, entryFromAuthenticator(en.Name, en.Auth, en.Hotkey, en.IconKey))
 	}
 	return out
 }
@@ -285,7 +291,7 @@ func (st *appState) absorbConfig(cfg *config.Config) {
 			global.Log.WithField("func", fn).WithError(err).Warn("skip entry")
 			continue
 		}
-		st.entries = append(st.entries, &entry{Name: e.Name, Auth: a, Hotkey: e.Hotkey})
+		st.entries = append(st.entries, &entry{Name: e.Name, Auth: a, Hotkey: e.Hotkey, IconKey: e.IconName})
 	}
 }
 
@@ -305,7 +311,7 @@ func (st *appState) mergeImportedConfig(cfg *config.Config) {
 			global.Log.WithField("func", fn).WithError(err).Warn("skip imported entry")
 			continue
 		}
-		st.entries = append(st.entries, &entry{Name: e.Name, Auth: a, Hotkey: e.Hotkey})
+		st.entries = append(st.entries, &entry{Name: e.Name, Auth: a, Hotkey: e.Hotkey, IconKey: e.IconName})
 	}
 }
 
@@ -608,8 +614,13 @@ func drawFrame(gtx layout.Context, th *material.Theme, st *appState, w *app.Wind
 			if added != nil {
 				st.mu.Lock()
 				st.entries = append(st.entries, &entry{Name: name, Auth: added})
+				idx := len(st.entries) - 1
 				st.mu.Unlock()
 				st.store.Push()
+				// Auto-open icon picker so the user can choose a brand
+				// icon for the entry right after adding it.
+				st.rowTargetIdx = idx
+				st.iconPickerDlg = newIconPickerDialog("")
 			}
 			st.dialog = nil
 			w.Invalidate()
@@ -656,6 +667,14 @@ func drawFrame(gtx layout.Context, th *material.Theme, st *appState, w *app.Wind
 				st.moveEntry(idx, -1)
 			case rowActionMoveDown:
 				st.moveEntry(idx, +1)
+			case rowActionChangeIcon:
+				st.mu.Lock()
+				current := ""
+				if idx >= 0 && idx < len(st.entries) {
+					current = st.entries[idx].IconKey
+				}
+				st.mu.Unlock()
+				st.iconPickerDlg = newIconPickerDialog(current)
 			}
 			w.Invalidate()
 		} else {
@@ -680,6 +699,20 @@ func drawFrame(gtx layout.Context, th *material.Theme, st *appState, w *app.Wind
 			w.Invalidate()
 		})
 	}
+	if st.iconPickerDlg != nil {
+		return st.iconPickerDlg.Layout(gtx, th, func(iconKey string, cancel bool) {
+			if !cancel {
+				st.mu.Lock()
+				if st.rowTargetIdx >= 0 && st.rowTargetIdx < len(st.entries) {
+					st.entries[st.rowTargetIdx].IconKey = iconKey
+				}
+				st.mu.Unlock()
+				st.store.Push()
+			}
+			st.iconPickerDlg = nil
+			w.Invalidate()
+		})
+	}
 
 	if st.tradesDialog != nil {
 		return st.tradesDialog.Layout(gtx, th)