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/UploadModelUrlInput.vue

@@ -20,7 +20,7 @@
                 :href="civitaiUrl"
                 target="_blank"
                 rel="noopener noreferrer"
-                class="text-muted underline"
+                class="text-muted-foreground underline"
               >
                 {{ $t('assetBrowser.providerCivitai') }}</a
               ><span>,</span>
@@ -35,7 +35,7 @@
                 :href="huggingFaceUrl"
                 target="_blank"
                 rel="noopener noreferrer"
-                class="text-muted underline"
+                class="text-muted-foreground underline"
               >
                 {{ $t('assetBrowser.providerHuggingFace') }}
               </a>
@@ -58,7 +58,7 @@
             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>
         <p v-else-if="!flags.asyncModelUploadEnabled" class="text-foreground">