feat(i18n): localize status messages and UI elements across various tools

src/pages/pdf-to-json.html

@@ -158,7 +158,12 @@
           <!-- File Display Area -->
           <div id="fileList" class="mt-4 hidden"></div>
 
-          <button id="convertBtn" disabled class="btn-gradient w-full mt-6">
+          <button
+            id="convertBtn"
+            disabled
+            class="btn-gradient w-full mt-6"
+            data-i18n="tools:pdfToJson.convertButton"
+          >
             Convert to JSON
           </button>
         </div>