feat(i18n): add Khmer language support

Register Khmer (km) locale, add complete 1,394-entry dashboard translation,
and show the Cambodia flag in the language selector. Place Khmer immediately
before Thai in the selector and keep the header locale in sync after switching.

src/i18n/config.js

@@ -20,6 +20,7 @@ export const LOCALES = [
   "uk",
   "tl",
   "id",
+  "km",
   "th",
   "hi",
   "bn",
@@ -60,6 +61,7 @@ export const LOCALE_NAMES = {
   tl: "Tagalog",
   id: "Indonesia",
   th: "ไทย",
+  km: "ខ្មែរ",
   hi: "हिन्दी",
   bn: "বাংলা",
   ur: "اردو",
@@ -141,6 +143,9 @@ export function normalizeLocale(locale) {
   if (locale === "th") {
     return "th";
   }
+  if (locale === "km") {
+    return "km";
+  }
   if (locale === "hi") {
     return "hi";
   }

src/shared/components/LanguageSwitcher.js

@@ -39,6 +39,7 @@ const getLocaleInfo = (locale) => {
     "tl": { name: "Tagalog", flag: "🇵🇭" },
     "id": { name: "Indonesia", flag: "🇮🇩" },
     "th": { name: "ไทย", flag: "🇹🇭" },
+    "km": { name: "ខ្មែរ", flag: "🇰🇭" },
     "hi": { name: "हिन्दी", flag: "🇮🇳" },
     "bn": { name: "বাংলা", flag: "🇧🇩" },
     "ur": { name: "اردو", flag: "🇵🇰" },
@@ -63,9 +64,9 @@ export default function LanguageSwitcher({ className = "", isOpen: controlledOpe
 
   const isControlled = typeof controlledOpen === "boolean";
   const isOpen = isControlled ? controlledOpen : internalOpen;
-  const setIsOpen = (value) => {
+  const setIsOpen = (value, nextLocale = locale) => {
     if (isControlled) {
-      if (!value && onClose) onClose(locale);
+      if (!value && onClose) onClose(nextLocale);
     } else {
       setInternalOpen(value);
     }
@@ -92,7 +93,6 @@ export default function LanguageSwitcher({ className = "", isOpen: controlledOpe
     if (nextLocale === locale || isPending) return;
 
     setIsPending(true);
-    setIsOpen(false);
     try {
       await fetch("/api/locale", {
         method: "POST",
@@ -103,6 +103,7 @@ export default function LanguageSwitcher({ className = "", isOpen: controlledOpe
       // Reload translations without full page reload
       await reloadTranslations();
       setLocale(nextLocale);
+      setIsOpen(false, nextLocale);
     } catch (err) {
       console.error("Failed to set locale:", err);
     } finally {

src/shared/constants/locales.js

@@ -22,6 +22,7 @@ export const LOCALE_FLAGS = {
   "tl": "🇵🇭",
   "id": "🇮🇩",
   "th": "🇹🇭",
+  "km": "🇰🇭",
   "hi": "🇮🇳",
   "bn": "🇧🇩",
   "ur": "🇵🇰",