Localizes language names in the language pie chart

Uses `Intl.DisplayNames` to display localized language names in the language pie chart, enhancing user experience and readability.

Also converts country and language values from the CSV data to ISO codes for standardization and improved data handling.
Adds tooltip to display ISO language code.

components/Charts.tsx

@@ -173,7 +173,26 @@ export function LanguagePieChart({ languages }: LanguagePieChartProps) {
       topLanguages.push(["Other", otherCount]);
     }
 
-    const labels = topLanguages.map(([lang]) => lang);
+    // Use Intl.DisplayNames to get localized language names from ISO codes
+    const languageDisplayNames = new Intl.DisplayNames(["en"], {
+      type: "language",
+    });
+
+    // Store original ISO codes for tooltip
+    const isoCodes = topLanguages.map(([lang]) => lang);
+
+    const labels = topLanguages.map(([lang], index) => {
+      // Check if this is a valid ISO 639-1 language code
+      if (lang && lang !== "Other" && /^[a-z]{2}$/.test(lang)) {
+        try {
+          return languageDisplayNames.of(lang);
+        } catch (e) {
+          return lang; // Fallback to code if display name can't be resolved
+        }
+      }
+      return lang; // Return original string for "Other" or invalid codes
+    });
+
     const data = topLanguages.map(([, count]) => count);
 
     const chart = new Chart(ctx, {
@@ -205,6 +224,27 @@ export function LanguagePieChart({ languages }: LanguagePieChartProps) {
               padding: 20,
             },
           },
+          tooltip: {
+            callbacks: {
+              label: function (context) {
+                const label = context.label || "";
+                const value = context.formattedValue || "";
+                const index = context.dataIndex;
+                const isoCode = isoCodes[index];
+
+                // Only show ISO code if it's not "Other" and it's a valid 2-letter code
+                if (
+                  isoCode &&
+                  isoCode !== "Other" &&
+                  /^[a-z]{2}$/.test(isoCode)
+                ) {
+                  return `${label} (${isoCode.toUpperCase()}): ${value}`;
+                }
+
+                return `${label}: ${value}`;
+              },
+            },
+          },
         },
       },
     });