Release 0.6.0

Bump __version__ per ADR-007; roll Unreleased into the 0.6.0
changelog section. Covers the machines rename (ADR-011), the
measuringtools plugin, per-plugin migrations (ADR-008), route
gating (ADR-009), the get_reports hook (contract 0.6.0), and
the sister-site adoption docs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shopdb/__init__.py

@@ -24,9 +24,9 @@ __contract_version__ = '0.6.0'
 
 # Product release version (see ADR-007). The product version and the
 # plugin-contract version above are distinct series with independent
-# bump rules; they happen to coincide at 0.5.0. Not part of the
-# shopdb.api contract surface, so it is not re-exported there.
-__version__ = '0.5.0'
+# bump rules. Not part of the shopdb.api contract surface, so it is
+# not re-exported there.
+__version__ = '0.6.0'
 
 
 def create_app(config_name: str = None) -> Flask: