(release) Prepare 1.0.0 release metadata

Add the initial 1.0.0 changelog, bump the package/application version,
and expose the release version through `pobsync --version`.

Cover the version output in the console entrypoint tests.

CHANGELOG.md

@@ -0,0 +1,29 @@
+# Changelog
+
+## 1.0.0 - 2026-05-21
+
+Initial stable release of the Django-first pobsync control panel.
+
+### Added
+
+- Django control panel for hosts, global settings, schedules, SSH credentials, snapshots, runs, self-checks, and logs.
+- Native systemd installer and updater for production backup servers.
+- SQLite by default, with optional MariaDB support.
+- Scheduler and worker services for queued manual backups and scheduled backups.
+- Manual backup, dry-run, cancellation, verbose rsync logging, and run detail views.
+- Snapshot discovery for existing backup directories and SQL-backed snapshot records.
+- SQL retention planning and apply flow with base snapshot protection and incomplete snapshot visibility.
+- Dashboard and host pages with backup health, latest run/snapshot, next run, and storage/stat summaries.
+- Restore guidance on snapshot detail pages.
+
+### Changed
+
+- Django and the database are now the source of truth for configuration.
+- Docker Compose is documented as development and disposable test tooling rather than the primary production path.
+- The `pobsync` console entrypoint is now a maintainer layer around Django management commands.
+
+### Removed
+
+- Legacy YAML config import/export workflow.
+- Public short aliases for configuration commands.
+- Obsolete global config storage fields.