Animate the splash and fix the web preview hanging on the logo

The splash now raises the sun in the mark and over a painted valley, floats
four feature chips around the mark, shimmers the wordmark, shows a three-beat
"how it works" card, drifts light motes upward and walks a status line
through the session check. A tap skips it.

The web build hung on the native splash because the asset manifest could not
be published: "assets/icons/splash_orb.png" is 27 characters, so its length
prefix in AssetManifest.bin is an ESC byte. Renamed it to splash_mark.png and
removed the unused anchor assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/assets/icons/logo.svg

@@ -1,17 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="512" height="512">
-  <!-- Grounded mark: a horizon line with a weight resting on it. The bar is
-       the ground; the block is what you are carrying. -->
-  <rect width="512" height="512" fill="#141414"/>
-
-  <!-- The block -->
-  <rect x="176" y="146" width="160" height="160" rx="34" fill="#EDEEEA"/>
-
-  <!-- The notch — a debt taken out of the block -->
-  <rect x="236" y="146" width="40" height="86" rx="20" fill="#141414"/>
-
-  <!-- The ground line -->
-  <rect x="120" y="348" width="272" height="26" rx="13" fill="#2F6F4E"/>
-
-  <!-- Shadow beneath, shortened: the weight sits on the line -->
-  <rect x="168" y="396" width="176" height="14" rx="7" fill="#EDEEEA" opacity="0.22"/>
-</svg>