fix(ui): correct CSS visibility typo; clean up spelling/grammar across codebase (#4661)

# Description of Changes

**What was changed**
- Fixed a CSS typo in `imageHighlighter.css` (`visbility` →
`visibility`) to restore the intended transition behavior.
- Corrected spelling/grammar in logs, comments, and console messages:
  - `PdfUtils.java`: log message “overlayed” → “overlaid”.
  - `CustomPDFDocumentFactoryTest.java`: comment typo “neeed” → “need”.
  - `FlattenController.java`: comment “readd” → “re-add”.
  - `PdfContainer.js`: console log “Hidding” → “Hiding”.
  - `navbar.js`: clarified tooltip comment wording.
  - `languages.html`: corrected Vietnamese label to “Tiếng Việt”.
- `ConvertWebsiteToPdfTest.java`: converted/de-duplicated comments to
clear English and improved assertion messages.
- No functional code paths altered except the CSS fix; the rest are
non-functional text improvements (logs/comments/tests/labels).

**Why the change was made**
- The CSS typo prevented the `visibility` transition from working as
intended.
- Consistent, correct wording improves developer experience, test
readability, and UI polish (language list).

---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Reece Browne <74901996+reecebrowne@users.noreply.github.com>

app/common/src/main/java/stirling/software/common/util/PdfUtils.java

@@ -567,7 +567,7 @@ public class PdfUtils {
                 PDImageXObject image = PDImageXObject.createFromByteArray(document, imageBytes, "");
                 // Draw the image onto the page at the specified x and y coordinates
                 contentStream.drawImage(image, x, y);
-                log.info("Image successfully overlayed onto PDF");
+                log.info("Image successfully overlaid onto PDF");
                 if (!everyPage && i == 0) {
                     break;
                 }

app/common/src/test/java/stirling/software/common/service/CustomPDFDocumentFactoryTest.java

@@ -117,7 +117,7 @@ class CustomPDFDocumentFactoryTest {
         }
     }
 
-    // neeed to add password pdf
+    // need to add password pdf
     //    @Test
     //    void testLoadPasswordProtectedPdfFromInputStream() throws IOException {
     //        try (InputStream is = getClass().getResourceAsStream("/protected.pdf")) {

app/core/src/main/java/stirling/software/SPDF/controller/api/misc/FlattenController.java

@@ -62,7 +62,7 @@ public class FlattenController {
             return WebResponseUtils.pdfDocToWebResponse(
                     document, Filenames.toSimpleFileName(file.getOriginalFilename()));
         } else {
-            // flatten whole page aka convert each page to image and readd it (making text
+            // flatten whole page aka convert each page to image and re-add it (making text
             // unselectable)
             PDFRenderer pdfRenderer = new PDFRenderer(document);
             PDDocument newDocument =

app/core/src/main/resources/static/css/imageHighlighter.css

@@ -8,7 +8,7 @@
   align-items: center;
   justify-content: center;
   transition:
-    visbility 0.1s linear,
+    visibility 0.1s linear,
     background-color 0.1s linear;
 }
 

app/core/src/main/resources/static/js/multitool/PdfContainer.js

@@ -731,7 +731,7 @@ class PdfContainer {
         this.showButton(selectIcon, true);
       }
     } else {
-      console.log("Page Select off. Hidding buttons");
+      console.log("Page Select off. Hiding buttons");
       this.showButton(selectIcon, false);
       this.showButton(deselectIcon, false);
     }

app/core/src/main/resources/static/js/navbar.js

@@ -110,7 +110,7 @@ function tooltipSetup() {
     element.addEventListener("mousemove", (event) => updateTooltipPosition(event, tooltipText));
     element.addEventListener("mouseleave", hideTooltip);
 
-    // in case UI moves and mouseleave is not triggered, tooltip is readded when mouse is moved over the element
+    // in case UI moves and mouseleave is not triggered, the tooltip is re-added when the mouse is moved over the element
     element.addEventListener("click", hideTooltip);
   });
 };

app/core/src/main/resources/templates/fragments/languages.html

@@ -38,7 +38,7 @@
      <div th:replace="~{fragments/languageEntry :: languageEntry ('hr_HR', 'Hrvatski')}"></div>
      <div th:replace="~{fragments/languageEntry :: languageEntry ('no_NB', 'Norsk')}"></div>
      <div th:replace="~{fragments/languageEntry :: languageEntry ('th_TH', 'ไทย')}"></div>
-     <div th:replace="~{fragments/languageEntry :: languageEntry ('vi_VN', 'Tiếng Việt')}"></div>
+     <div th:replace="~{fragments/languageEntry :: languageEntry ('vi_VN', 'Tiếng Việt')}"></div>
      <div th:replace="~{fragments/languageEntry :: languageEntry ('ml_IN', 'മലയാളം')}"></div>
      
 </th:block>

app/core/src/test/java/stirling/software/SPDF/controller/api/converters/ConvertWebsiteToPdfTest.java

@@ -225,8 +225,8 @@ public class ConvertWebsiteToPdfTest {
         UrlToPdfRequest request = new UrlToPdfRequest();
         request.setUrlInput("https://example.com");
 
-        Path preCreatedTemp = java.nio.file.Files.createTempFile("test_output_", ".pdf");
-        Path htmlTemp = java.nio.file.Files.createTempFile("test_input_", ".html");
+        Path preCreatedTemp = Files.createTempFile("test_output_", ".pdf");
+        Path htmlTemp = Files.createTempFile("test_input_", ".html");
 
         try (MockedStatic<GeneralUtils> gu = Mockito.mockStatic(GeneralUtils.class);
                 MockedStatic<ProcessExecutor> pe = Mockito.mockStatic(ProcessExecutor.class);
@@ -271,12 +271,12 @@ public class ConvertWebsiteToPdfTest {
             assertNotNull(resp, "Response should not be null");
             assertEquals(HttpStatus.OK, resp.getStatusCode());
             assertTrue(
-                    java.nio.file.Files.exists(preCreatedTemp),
+                    Files.exists(preCreatedTemp),
                     "Temp file should still exist despite delete IOException");
         } finally {
             try {
-                java.nio.file.Files.deleteIfExists(preCreatedTemp);
-                java.nio.file.Files.deleteIfExists(htmlTemp);
+                Files.deleteIfExists(preCreatedTemp);
+                Files.deleteIfExists(htmlTemp);
             } catch (IOException ignore) {
             }
         }