packaging(debian-upstream): polish Debian packaging for Debian Policy compliance

[satwareAG-ironMike]

Context

Debian has strict packaging policies (Debian Policy Manual, Debian Developer Reference). The packaging skeleton from Phase 1 needs polish to meet these standards before a Debian Maintainer will sponsor the upload.

This includes: proper debian/watch file, debian/copyright in machine-readable format, debian/compat version, multi-arch support, dpkg-buildpackage passing piuparts and lintian --pedantic clean.

Acceptance Criteria

• debian/watch file exists (watches GitHub releases for new versions)
• debian/copyright in DEP-5 machine-readable format
• debian/compat = 13 (debhelper compat level)
• lintian --pedantic --info — no errors, no warnings
• piuparts passes (install + purge test)
• Multi-Arch: foreign declared (extension is arch-specific but coinstallable)
• debian/rules follows debhelper pattern (no custom make calls outside override_dh_*)
• debian/tests/ directory with autopkgtest smoke test
• Package builds reproducibly (SOURCE_DATE_EPOCH respected)

Dependencies

• Bug: Column alias deduplication fails on padded aliases (Firebird 3.0) #23 (ITP filed) — Debian team must be aware of the intent
• All Phase 1-3 complete

Suggested Test Plan

1. lintian --pedantic *.deb — zero errors, zero warnings
2. piuparts *.deb — passes
3. dpkg-source --commit — clean source package
4. sbuild --arch-all — builds on multiple architectures
5. autopkgtest *.deb — smoke test passes