Add comprehensive test for lang resource and flag existence (#1643)

## Description:

Checks that each lang file’s lang_code matches its filename and that the
flag SVG exists.
Reports all errors in a single test run for easier debugging.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I have read and accepted the CLA agreement (only required once).

## Please put your Discord username so you can be contacted if a bug or
regression is found:

aotumuri

Co-authored-by: Drills Kibo <59177241+drillskibo@users.noreply.github.com>

tests/LangSvg.test.ts

@@ -0,0 +1,53 @@
+import fs from "fs";
+import path from "path";
+
+describe("Lang SVG Field and File Existence Check", () => {
+  const langDir = path.join(__dirname, "../resources/lang");
+  const flagDir = path.join(__dirname, "../resources/flags");
+
+  test("each lang.json file has a valid lang.svg string and the SVG file exists", () => {
+    const files = fs
+      .readdirSync(langDir)
+      .filter((file) => file.endsWith(".json"));
+
+    if (files.length === 0) {
+      console.log("No resources/lang/*.json files found. Skipping check.");
+      return;
+    }
+
+    const errors: string[] = [];
+
+    for (const file of files) {
+      try {
+        const filePath = path.join(langDir, file);
+        const jsonData = JSON.parse(fs.readFileSync(filePath, "utf-8"));
+        const langSvg = jsonData.lang?.svg;
+        if (typeof langSvg !== "string" || langSvg.length === 0) {
+          errors.push(
+            `[${file}]: lang.svg is missing or not a non-empty string`,
+          );
+          continue;
+        }
+
+        // Check if the SVG file exists in the flags directory
+        const svgFile = langSvg.endsWith(".svg") ? langSvg : `${langSvg}.svg`;
+        const flagPath = path.join(flagDir, svgFile);
+
+        if (!fs.existsSync(flagPath)) {
+          errors.push(`[${file}]: SVG file does not exist: ${svgFile}`);
+        }
+      } catch (err) {
+        errors.push(
+          `[${file}]: Exception occurred - ${(err as Error).message}`,
+        );
+      }
+    }
+
+    if (errors.length > 0) {
+      console.error(
+        "Lang SVG field or file check failed:\n" + errors.join("\n"),
+      );
+      expect(errors).toEqual([]);
+    }
+  });
+});