fix(packaging): .deb and .rpm of a beta sort before the final release (#1494)

[ZhuchkaTriplesix]

Closes #1494. Part of the Beta channel epic #1499.

build_deb.sh wrote Version: 0.5.0-beta.1, which dpkg reads as upstream 0.5.0 with revision beta.1, newer than 0.5.0; build_rpm.sh wrote 0.5.0.beta.1, also newer than 0.5.0. Beta users would never be upgraded to the final package.

• scripts/linux/package_version.sh maps the pubspec version to the package version: the first - becomes ~ (which both dpkg and rpm sort before anything, even the end of the string), any further - becomes . (it would otherwise start a Debian revision or an RPM release). 0.5.0-beta.1 → 0.5.0~beta.1; a final 0.5.0 is unchanged.
• build_deb.sh and build_rpm.sh use it for Version: / %{version}. The file names keep the tag form (Querya-Desktop-0.5.0-beta.1-linux.deb), so the updater's asset rules and SHA256SUMS.txt are unaffected.
• Windows: AppVersion in querya.iss is free text and no VersionInfoVersion is derived from it, so -beta.1 is accepted. macOS takes the version from Flutter's build name; whether CFBundleShortVersionString with -beta.1 is accepted (and notarized) needs the dry run from ci(release): beta tags publish a pre-release, not latest, and skip AUR / APT / DNF #1492.

Behaviour change worth knowing: an old marketing suffix such as 0.4.11-b now becomes 0.4.11~b, which sorts before 0.4.11 (SemVer reading) instead of after it.

Tests (test/packaging/): the mapping; and, where the tools exist, that 0.4.19 < 0.5.0-beta.1 < 0.5.0-beta.2 < 0.5.0-beta.10 < 0.5.0 < 0.5.1 holds for dpkg --compare-versions (present on the Ubuntu CI runners) and for rpm.vercmp (skipped when rpm is not installed).