feat(pwa): create native PWA manifest.json

Story 1: Create Native PWA Manifest
- Extract manifest configuration from vite.config.ts to static/manifest.json
- Preserve exact configuration including share_target for Instagram URLs
- Update app.html to reference new manifest.json location
- Validated JSON syntax successfully

All PWA properties maintained:
- Share target: /share route for external app sharing
- Icons: favicon.png in 192x192 and 512x512 sizes
- Display: standalone mode for PWA installation
- Theme colors: white background and theme colors

Refs: docs/plans/MigrateToNativeSvelteKitPWA.md

secrets/auth.json

@@ -5,7 +5,7 @@
       "value": "SDRORLyWEsWWty2ZoVGdER",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1800935502.281271,
+      "expires": 1800936907.11208,
       "httpOnly": false,
       "secure": true,
       "sameSite": "Lax"
@@ -45,7 +45,7 @@
       "value": "59661903731",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1774151502.281377,
+      "expires": 1774152907.11217,
       "httpOnly": false,
       "secure": true,
       "sameSite": "None"
@@ -55,7 +55,7 @@
       "value": "1280x720",
       "domain": ".instagram.com",
       "path": "/",
-      "expires": 1766980302,
+      "expires": 1766981708,
       "httpOnly": false,
       "secure": true,
       "sameSite": "Lax"
@@ -72,7 +72,7 @@
     },
     {
       "name": "rur",
-      "value": "\"CLN\\05459661903731\\0541797911502:01fe38d640e1e65ff57f8cb338b26d9ad276f995f2219f37928cf62a120e539a0970aee9\"",
+      "value": "\"CLN\\05459661903731\\0541797912907:01feab225fa86f00b6be5c6aad172798799c1d3bf81b1dcd57e6fc8313e49aa6b9899a74\"",
       "domain": ".instagram.com",
       "path": "/",
       "expires": -1,
@@ -87,7 +87,7 @@
       "localStorage": [
         {
           "name": "chatd-deviceid",
-          "value": "b5c8e400-9eff-4ae0-879e-558a387dc609"
+          "value": "959def05-6e66-4805-8316-d9fdd4cd4f95"
         },
         {
           "name": "hb_timestamp",
@@ -95,7 +95,11 @@
         },
         {
           "name": "IGSession",
-          "value": "kc8y0b:1766377302597"
+          "value": "kc8y0b:1766378707663"
+        },
+        {
+          "name": "mutex_polaris_banzai",
+          "value": "8ort9t:1766376779950"
         },
         {
           "name": "pixel_fire_ts",
@@ -107,12 +111,16 @@
         },
         {
           "name": "Session",
-          "value": "jdpnmy:1766375537597"
+          "value": "b8iamu:1766376942663"
         },
         {
           "name": "has_interop_upgraded",
           "value": "{\"lastCheckedAt\":1766366944051,\"status\":false}"
         },
+        {
+          "name": "mutex_banzai",
+          "value": "8ort9t:1766376779950"
+        },
         {
           "name": "banzai:last_storage_flush",
           "value": "1766366944520.7"