[v-byte-cpu]

Why

The initial plugin exposed a limited Feed view. This change brings the
backend's reading and management capabilities into a complete plugin UI.

What Changed

• Implement the responsive shell and Feed, Search, Reader, Digests, Tasks
  and Settings screens with the shared peach design system.
• Add explicit AI summaries, consent-based image loading and independent
  Compact/Full Vault Snapshots with protected writes and rollback.
• Introduce generated OpenAPI types, device-local connections,
  vault preferences and lifecycle-owned resource cleanup.
• Connect advisory SSE with bounded reconnect and authoritative REST
  reconciliation; enable configurable backend CORS through Echo.
• Add Storybook, mobile dependency checks and headless Obsidian CI gates.
• Update product, design, development and release documentation.