Release OpenChat desktop 0.8.48

[MinionEnjoyer]

Summary

• bump desktop, web, API, tests, and maintained documentation to 0.8.48
• reject desktop release tags when the configured server URL is missing or not HTTPS
• verify the server URL remains injected into every desktop build

Verification

• API: 46 suites / 308 tests passed; Nest build passed
• Web: 27 files / 71 tests passed; Vite production build passed
• Documentation consistency verifier passed
• repository and history secret scan passed
• production API health, OpenChat-to-OpenShare upload, and LiveKit WebRTC probes passed
• local Tauri compile was unavailable because Rust is not installed; GitHub's signed platform matrix remains the authoritative desktop build gate