perf: lazy load ical.js to reduce initial bundle size

Move ical.js (~76KB) to a lazy-loaded chunk via dynamic import.
The library is only loaded when calendar integration features are used.

- Create ical-lazy-loader.ts for on-demand loading
- Make getRelevantEventsForCalendarIntegrationFromIcal async
- Update calendar-integration.service.ts to use switchMap

package-lock.json

@@ -1171,18 +1171,6 @@
         }
       }
     },
-    "node_modules/@angular/build/node_modules/@types/node": {
-      "version": "25.0.3",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.0.3.tgz",
-      "integrity": "sha512-W609buLVRVmeW693xKfzHeIV6nJGGz98uCPfeXI1ELMLXVeKYZ9m15fAMSaUPBHYLGFsVRcMmSCksQOrZV9BYA==",
-      "dev": true,
-      "license": "MIT",
-      "optional": true,
-      "peer": true,
-      "dependencies": {
-        "undici-types": "~7.16.0"
-      }
-    },
     "node_modules/@angular/build/node_modules/@vitejs/plugin-basic-ssl": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/@vitejs/plugin-basic-ssl/-/plugin-basic-ssl-2.1.0.tgz",
@@ -1196,15 +1184,6 @@
         "vite": "^6.0.0 || ^7.0.0"
       }
     },
-    "node_modules/@angular/build/node_modules/undici-types": {
-      "version": "7.16.0",
-      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.16.0.tgz",
-      "integrity": "sha512-Zz+aZWSj8LE6zoxD+xrjh4VfkIG8Ya6LvYkZqtUQGJPZjYl53ypCaUwWqo7eI0x66KBGeRo+mlBEkMSeSZ38Nw==",
-      "dev": true,
-      "license": "MIT",
-      "optional": true,
-      "peer": true
-    },
     "node_modules/@angular/build/node_modules/vite": {
       "version": "7.1.11",
       "resolved": "https://registry.npmjs.org/vite/-/vite-7.1.11.tgz",
@@ -13692,6 +13671,16 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/encoding": {
+      "version": "0.1.13",
+      "resolved": "https://registry.npmjs.org/encoding/-/encoding-0.1.13.tgz",
+      "integrity": "sha512-ETBauow1T35Y/WZMkio9jiM0Z5xjHHmJ4XmjZOq1l/dXz3lr2sRn87nJy20RupqSh1F2m3HHPSp8ShIPQJrJ3A==",
+      "license": "MIT",
+      "optional": true,
+      "dependencies": {
+        "iconv-lite": "^0.6.2"
+      }
+    },
     "node_modules/end-of-stream": {
       "version": "1.4.4",
       "dev": true,
@@ -16397,7 +16386,7 @@
     },
     "node_modules/iconv-lite": {
       "version": "0.6.3",
-      "dev": true,
+      "devOptional": true,
       "license": "MIT",
       "dependencies": {
         "safer-buffer": ">= 2.1.2 < 3.0.0"
@@ -22623,7 +22612,7 @@
     },
     "node_modules/safer-buffer": {
       "version": "2.1.2",
-      "dev": true,
+      "devOptional": true,
       "license": "MIT"
     },
     "node_modules/sanitize-filename": {