feat(calendar): show regional holidays and observances

public/locales/en.json

@@ -367,7 +367,47 @@
     "emptyDay": "No memories or milestones recorded for this day.",
     "openToday": "Write a memory",
     "writeMemory": "Add memory",
-    "openTasks": "Open tasks"
+    "openTasks": "Open tasks",
+    "holidayCountry": "Country / region",
+    "autoCountry": "Auto ({country})",
+    "publicHoliday": "Public holiday",
+    "festival": "Festival",
+    "workingDay": "Working day",
+    "observed": "Substitute day off",
+    "estimated": "Date is estimated",
+    "workingWeekend": "Official working weekend",
+    "loadingHolidays": "Loading holidays…",
+    "holidayUnavailable": "Holiday data unavailable.",
+    "retryHolidays": "Retry",
+    "holidaySource": "Public holiday data",
+    "outsideRange": "Holiday data covers 2024–2030.",
+    "festivals": {
+      "valentine": "Valentine’s Day",
+      "earth": "Earth Day",
+      "halloween": "Halloween",
+      "christmasEve": "Christmas Eve",
+      "teachers": "Teachers’ Day"
+    },
+    "holidayNames": {
+      "New Year's Day": "New Year's Day",
+      "Chinese New Year (Spring Festival)": "Chinese New Year (Spring Festival)",
+      "Chinese New Year": "Chinese New Year",
+      "Chinese New Year's Eve": "Chinese New Year's Eve",
+      "Tomb-Sweeping Day": "Tomb-Sweeping Day",
+      "Labor Day": "Labor Day",
+      "Dragon Boat Festival": "Dragon Boat Festival",
+      "Mid-Autumn Festival": "Mid-Autumn Festival",
+      "National Day": "National Day",
+      "Christmas Day": "Christmas Day",
+      "Christmas Eve": "Christmas Eve",
+      "Good Friday": "Good Friday",
+      "Easter Monday": "Easter Monday",
+      "Peace Memorial Day": "Peace Memorial Day",
+      "Children's Day": "Children's Day",
+      "Constitution Day": "Constitution Day",
+      "Confucius' Birthday": "Confucius' Birthday"
+    },
+    "holidayCaveat": "Dates may change; check local official announcements."
   },
   "tasks": {
     "eyebrow": "GOALS & TASKS",