feat(ui): animated boot splash and loading screen

Show a Lottie-animated splash while the app bundle boots and dismiss it
once WebAppComponent initialises, plus a reusable mifosx-loading-screen
component with loading and error animations. lottie.min.js is served
from the lottie-web package instead of being vendored into src/assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -71,6 +71,7 @@
     "jspdf-autotable": "^5.0.2",
     "lightgallery": "^2.9.0",
     "lodash": "4.17.23",
+    "lottie-web": "^5.13.0",
     "moment": "^2.29.4",
     "ngx-image-cropper": "^9.1.6",
     "ngx-mat-select-search": "^8.0.2",