fix(upload-model): UI/UX improvements for Upload Model Dialog (#7969)

## Summary

Addresses UI/UX feedback on the Upload Model Dialog (BYOM feature).

## Changes

1. **Standardize link styling** - Use consistent `text-muted-foreground
underline` for all links in both URL input variants
2. **Increase warning/example text font size** - Changed from 12px
(`text-xs`) to 14px (`text-sm`) for better readability
3. **Fix padding inconsistency** - Aligned padding between model name
box and SingleSelect dropdown; moved "Not sure?" help text inline with
the label
4. **Add "Upload Another" button** - Allows users to upload multiple
models without closing and reopening the dialog

## Testing

- Verified link styling consistency across both Civitai and generic URL
input components
- Confirmed padding alignment in confirmation step
- Tested Upload Another button resets wizard to step 1

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7969-fix-upload-model-UI-UX-improvements-for-Upload-Model-Dialog-2e66d73d3650815c8184cedb3d02672d)
by [Unito](https://www.unito.io)

src/platform/assets/components/UploadModelUrlInputCivitai.vue

@@ -11,7 +11,7 @@
               <a
                 href="https://civitai.com/models"
                 target="_blank"
-                class="text-muted-foreground"
+                class="text-muted-foreground underline"
               >
                 {{ $t('assetBrowser.uploadModelDescription2Link') }}
               </a>
@@ -51,14 +51,14 @@
           class="icon-[lucide--circle-check-big] absolute top-1/2 right-3 size-5 -translate-y-1/2 text-green-500"
         />
       </div>
-      <p v-if="error" class="text-xs text-error">
+      <p v-if="error" class="text-sm text-error">
         {{ error }}
       </p>
       <i18n-t
         v-else
         keypath="assetBrowser.civitaiLinkExample"
         tag="p"
-        class="text-xs"
+        class="text-sm"
       >
         <template #example>
           <strong>{{ $t('assetBrowser.civitaiLinkExampleStrong') }}</strong>
@@ -67,7 +67,7 @@
           <a
             href="https://civitai.com/models/10706/luisap-z-image-and-qwen-pixel-art-refiner?modelVersionId=2225295"
             target="_blank"
-            class="text-muted-foreground"
+            class="text-muted-foreground underline"
           >
             {{ $t('assetBrowser.civitaiLinkExampleUrl') }}
           </a>