refactor(ui): improve icon rendering consistency and spacing

Standardize icon sizes and improve rendering consistency across the
application interface.

Changes:
- ProviderIcon: Add fontSize sync with size prop for embedded SVG
  scaling, improve fallback text sizing calculation
- AppSwitcher: Replace brand icon components with unified ProviderIcon,
  standardize icon size to 20px across all app tabs
- ProviderCard: Reduce icon size from 26px to 20px for better visual
  balance in card layout
- DeepLinkImportDialog: Increase confirmation icon size from 64px to
  80px for better visibility
- BasicFormFields: Reduce icon picker button spacing from space-y-6 to
  space-y-2 for improved layout density

Icon rendering improvements:
- Embedded SVGs now properly scale with fontSize set to match size prop
- Fallback initials use responsive font sizing (50% of icon size,
  minimum 12px)
- Consistent 20px standard for navigation and card icons
- Better visual hierarchy with appropriate sizing for different contexts

This refactor improves visual consistency and makes icon rendering
more predictable across different components.

src/components/AppSwitcher.tsx

@@ -1,5 +1,5 @@
 import type { AppId } from "@/lib/api";
-import { ClaudeIcon, CodexIcon, GeminiIcon } from "./BrandIcons";
+import { ProviderIcon } from "@/components/ProviderIcon";
 
 interface AppSwitcherProps {
   activeApp: AppId;
@@ -11,6 +11,17 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
     if (app === activeApp) return;
     onSwitch(app);
   };
+  const iconSize = 20;
+  const appIconName: Record<AppId, string> = {
+    claude: "claude",
+    codex: "openai",
+    gemini: "gemini",
+  };
+  const appDisplayName: Record<AppId, string> = {
+    claude: "Claude",
+    codex: "Codex",
+    gemini: "Gemini",
+  };
 
   return (
     <div className="inline-flex bg-gray-100 dark:bg-gray-800 rounded-lg p-1 gap-1">
@@ -23,15 +34,17 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
             : "text-gray-500 hover:text-gray-900 hover:bg-white/50 dark:text-gray-400 dark:hover:text-gray-100 dark:hover:bg-gray-800/60"
         }`}
       >
-        <ClaudeIcon
-          size={16}
+        <ProviderIcon
+          icon={appIconName.claude}
+          name={appDisplayName.claude}
+          size={iconSize}
           className={
             activeApp === "claude"
               ? "text-foreground"
               : "text-gray-500 dark:text-gray-400 group-hover:text-foreground transition-colors"
           }
         />
-        <span>Claude</span>
+        <span>{appDisplayName.claude}</span>
       </button>
 
       <button
@@ -43,15 +56,17 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
             : "text-gray-500 hover:text-gray-900 hover:bg-white/50 dark:text-gray-400 dark:hover:text-gray-100 dark:hover:bg-gray-800/60"
         }`}
       >
-        <CodexIcon
-          size={16}
+        <ProviderIcon
+          icon={appIconName.codex}
+          name={appDisplayName.codex}
+          size={iconSize}
           className={
             activeApp === "codex"
               ? "text-foreground"
               : "text-gray-500 dark:text-gray-400 group-hover:text-foreground transition-colors"
           }
         />
-        <span>Codex</span>
+        <span>{appDisplayName.codex}</span>
       </button>
 
       <button
@@ -63,15 +78,17 @@ export function AppSwitcher({ activeApp, onSwitch }: AppSwitcherProps) {
             : "text-gray-500 hover:text-gray-900 hover:bg-white/50 dark:text-gray-400 dark:hover:text-gray-100 dark:hover:bg-gray-800/60"
         }`}
       >
-        <GeminiIcon
-          size={16}
+        <ProviderIcon
+          icon={appIconName.gemini}
+          name={appDisplayName.gemini}
+          size={iconSize}
           className={
             activeApp === "gemini"
               ? "text-foreground"
               : "text-gray-500 dark:text-gray-400 group-hover:text-foreground transition-colors"
           }
         />
-        <span>Gemini</span>
+        <span>{appDisplayName.gemini}</span>
       </button>
     </div>
   );

src/components/DeepLinkImportDialog.tsx

@@ -338,7 +338,7 @@ export function DeepLinkImportDialog() {
                       <ProviderIcon
                         icon={request.icon}
                         name={request.name || request.icon}
-                        size={64}
+                        size={80}
                         className="drop-shadow-sm"
                       />
                     </div>

src/components/ProviderIcon.tsx

@@ -32,6 +32,9 @@ export const ProviderIcon: React.FC<ProviderIconProps> = ({
     return {
       width: sizeValue,
       height: sizeValue,
+      // 内嵌 SVG 使用 1em 作为尺寸基准，这里同步 fontSize 让图标实际跟随 size 放大
+      fontSize: sizeValue,
+      lineHeight: 1,
     };
   }, [size]);
 
@@ -57,6 +60,8 @@ export const ProviderIcon: React.FC<ProviderIconProps> = ({
       .join("")
       .toUpperCase()
       .slice(0, 2);
+    const fallbackFontSize =
+      typeof size === "number" ? `${Math.max(size * 0.5, 12)}px` : "0.5em";
     return (
       <span
         className={cn(
@@ -68,7 +73,7 @@ export const ProviderIcon: React.FC<ProviderIconProps> = ({
       >
         <span
           style={{
-            fontSize: `${typeof size === "number" ? size * 0.4 : 14}px`,
+            fontSize: fallbackFontSize,
           }}
         >
           {initials}

src/components/providers/ProviderCard.tsx

@@ -141,12 +141,12 @@ export function ProviderCard({
           </button>
 
           {/* 供应商图标 */}
-          <div className="h-9 w-9 rounded-lg bg-white/5 flex items-center justify-center border border-gray-200 dark:border-white/10 group-hover:scale-105 transition-transform duration-300">
+          <div className="h-8 w-8 rounded-lg bg-white/5 flex items-center justify-center border border-gray-200 dark:border-white/10 group-hover:scale-105 transition-transform duration-300">
             <ProviderIcon
               icon={provider.icon}
               name={provider.name}
               color={provider.iconColor}
-              size={26}
+              size={20}
             />
           </div>
 

src/components/providers/forms/BasicFormFields.tsx

@@ -84,7 +84,7 @@ export function BasicFormFields({ form }: BasicFormFieldsProps) {
                 </div>
               </div>
               <div className="flex-1 overflow-y-auto">
-                <div className="space-y-6 mx-auto max-w-[56rem] px-6 py-6 w-full">
+                <div className="space-y-2 mx-auto max-w-[56rem] px-6 py-6 w-full">
                   <IconPicker
                     value={currentIcon}
                     onValueChange={handleIconSelect}