Prepare v1.0.0-rc.3 prerelease

[enaboapps]

Closes #675

Summary

• bump the frontend, Rust application, startup launcher, Tauri configuration, browser fallback, tests, and lockfiles to 1.0.0-rc.3
• retain the reviewed Windows GATT startup recovery fix now on main
• prepare the exact source commit for the signed prerelease workflow

Validation

• npm run lint
• npm test (74 frontend tests and 5 updater-feed tests)
• npm run build
• main Rust fmt, Clippy with warnings denied, 243 unit tests, and 7 configuration tests
• updater verifier fmt, Clippy, and 2 tests
• startup launcher fmt, Clippy, and 2 tests
• npm audit --audit-level=high (0 vulnerabilities)
• cargo-audit 0.22.2 against all three lockfiles (no vulnerabilities; existing allowed warnings only in the main graph)
• rebuilt the unsigned Windows UIAccess NSIS installer for 1.0.0-rc.3
• verified the application, launcher, and installer manifests with the development unsigned-artifact override