Use Temporal.PlainDate for absolute dates (#29804)

Use the upcoming
[Temporal.PlainDate](https://tc39.es/proposal-temporal/docs/plaindate.html)
via polyfill. If there is any remaining bugs in `<absolute-date>` this
will iron them out. I opted for the lightweight polyfill because both
seem to achieve our goal of localizeable absolute dates.

- With
[`@js-temporal/polyfill`](https://www.npmjs.com/package/@js-temporal/polyfill)
chunk size goes from 81.4 KiB to 274 KiB
- With
[`temporal-polyfill`](https://www.npmjs.com/package/temporal-polyfill)
chunk size goes from 81.4 KiB to 142 KiB

Also see [this
table](https://github.com/fullcalendar/temporal-polyfill?tab=readme-ov-file#comparison-with-js-temporalpolyfill)
for more comparisons of these polyfills. Soon there will be
[treeshakable
API](https://github.com/fullcalendar/temporal-polyfill?tab=readme-ov-file#tree-shakable-api)
as well which will further reduce size.

package-lock.json

@@ -47,6 +47,7 @@
         "sortablejs": "1.15.2",
         "swagger-ui-dist": "5.12.0",
         "tailwindcss": "3.4.1",
+        "temporal-polyfill": "0.2.3",
         "throttle-debounce": "5.0.0",
         "tinycolor2": "1.6.0",
         "tippy.js": "6.3.7",
@@ -11524,6 +11525,19 @@
         "node": ">=6"
       }
     },
+    "node_modules/temporal-polyfill": {
+      "version": "0.2.3",
+      "resolved": "https://registry.npmjs.org/temporal-polyfill/-/temporal-polyfill-0.2.3.tgz",
+      "integrity": "sha512-7ZJRc7wq/1XjrOQYkkNpgo2qfE9XLrUU8D/DS+LAC/T0bYqZ46rW6dow0sOTXTPZS4bwer8bD/0OyuKQBfA3yw==",
+      "dependencies": {
+        "temporal-spec": "^0.2.0"
+      }
+    },
+    "node_modules/temporal-spec": {
+      "version": "0.2.0",
+      "resolved": "https://registry.npmjs.org/temporal-spec/-/temporal-spec-0.2.0.tgz",
+      "integrity": "sha512-r1AT0XdEp8TMQ13FLvOt8mOtAxDQsRt2QU5rSWCA7YfshddU651Y1NHVrceLANvixKdf9fYO8B/S9fXHodB7HQ=="
+    },
     "node_modules/terser": {
       "version": "5.29.2",
       "resolved": "https://registry.npmjs.org/terser/-/terser-5.29.2.tgz",