chore: replace icons with user's design + clean old icon files

.gitattributes

@@ -1 +1,2 @@
 # Database downloaded at runtime from HF bucket — no LFS needed
+webapp/tipitaka-web/public/*.png filter=lfs diff=lfs merge=lfs -text

webapp/tipitaka-web/public/manifest.json

@@ -9,25 +9,25 @@
   "orientation": "any",
   "icons": [
     {
-      "src": "/pwa-icon-192.png",
+      "src": "/icon-192.png",
       "sizes": "192x192",
       "type": "image/png",
       "purpose": "any"
     },
     {
-      "src": "/pwa-icon-512.png",
+      "src": "/icon-512.png",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "any"
     },
     {
-      "src": "/pwa-icon-192.png",
+      "src": "/icon-192.png",
       "sizes": "192x192",
       "type": "image/png",
       "purpose": "maskable"
     },
     {
-      "src": "/pwa-icon-512.png",
+      "src": "/icon-512.png",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "maskable"