release: v0.1.0

[debpalash]

Summary

• promote Bootable directly to stable v0.1.0
• remove current alpha branding from the desktop app, installers, website, security guidance, and issue flow
• publish future tagged builds as normal releases instead of prereleases
• keep historical alpha entries in the changelog while making 0.1.0 the current release
• point downloads, checksums, provenance commands, and install defaults at stable artifacts

Verification

• cargo +1.98.0 fmt --all --check
• cargo +1.98.0 clippy --workspace --all-targets -- -D warnings
• cargo test --workspace (112 active tests passed; 3 intentionally ignored)
• cargo build --release --workspace
• release binary reports bootable 0.1.0
• npm run build --prefix site (14 routes)
• exact Pages canonical, sitemap, noindex, and v0.1.0 assertions
• shell installer syntax check

Launch

After this PR is green and merged, tag v0.1.0 to build, attest, and publish the stable release.