Polish store and v2rayA app for release

- Redesign store README as a minimal storefront

- Refine app README and remove technical clutter

- Update Sphera icon with refined vector styling

- Use original v2rayA app icon

- Use raw GitHub URL for v2rayA icon per Umbrel Community Store spec

- Add custom v2rayA image build for UmbrelOS nf_tables iptables

.gitignore

@@ -0,0 +1,12 @@
+# OS
+.DS_Store
+Thumbs.db
+
+# IDE
+.idea/
+.vscode/
+*.iml
+
+# Umbrel runtime data (should not be committed)
+**/data/*
+!**/.gitkeep