Issue 32-2: Establish visible v2.0.0 version

[gacurl]

Summary

Establish AssetTrack v2.0.0 as the current release baseline, display the version in the shared application UI, and document version/tag/SHA discipline for future deployments.

Related Issue

Closes #1200

Changes

• Added ASSETTRACK_VERSION = "2.0.0" as the single application version source.
• Exposed the version through the existing shared template context.
• Added AssetTrack v2.0.0 to the shared authenticated layout.
• Added focused shared-layout version coverage.
• Updated deployment documentation with SemVer, release-tag, and deployed-SHA requirements.
• Updated release notes to v2.0.0.

Verification

• Focused tests: 36 passed
• Full regression: 826 passed, 8 subtests passed
• git diff --check passed
• Docker rebuild completed
• Manual incognito browser verification completed
• Version displayed correctly on multiple authenticated pages
• No schema, persistence, auth, custody, event, dependency, or routing changes

Notes

Do not create the v2.0.0 Git tag until this PR is merged and the exact release commit on main is confirmed.