✨ feat: polish “Missing Models” UX & mobile actions layout

Overview
• Re-designed `MissingModelsModal` to align with `ModelTestModal` and deliver a cleaner, paginated experience.
• Improved mobile responsiveness for action buttons in `ModelsActions`.

Details
1. MissingModelsModal.jsx
   • Switched from `List` to `Table` for a more structured view.
   • Added search bar with live keyword filtering and clear icon.
   • Implemented pagination via `MODEL_TABLE_PAGE_SIZE`; auto-resets on search.
   • Dynamic rendering: when no data, show unified Empty state without column header.
   • Enhanced header layout with total-count subtitle and modal corner rounding.
   • Removed unused `Typography.Text` import.

2. ModelsActions.jsx
   • Set “Delete Selected Models” and “Missing Models” buttons to `flex-1 md:flex-initial`, placing them on the same row as “Add Model” on small screens.

Result
The “Missing Models” workflow now offers quicker discovery, a familiar table interface, and full mobile friendliness—without altering API behavior.

controller/missing_models.go

@@ -0,0 +1,27 @@
+package controller
+
+import (
+    "net/http"
+    "one-api/model"
+
+    "github.com/gin-gonic/gin"
+)
+
+// GetMissingModels returns the list of model names that are referenced by channels
+// but do not have corresponding records in the models meta table.
+// This helps administrators quickly discover models that need configuration.
+func GetMissingModels(c *gin.Context) {
+    missing, err := model.GetMissingModels()
+    if err != nil {
+        c.JSON(http.StatusOK, gin.H{
+            "success": false,
+            "message": err.Error(),
+        })
+        return
+    }
+
+    c.JSON(http.StatusOK, gin.H{
+        "success": true,
+        "data":    missing,
+    })
+}