Quilt3 v8.0.0 (#5166)

Major rather than minor: the queued changes drop Python 3.9 (EOL).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: sir-sigurd

api/python/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "uv_build"
 
 [project]
 name = "quilt3"
-version = "7.3.0"
+version = "8.0.0"
 description = "Quilt: where data comes together"
 readme = "README.rst"
 requires-python = ">=3.10"

api/python/uv.lock

@@ -16,7 +16,7 @@ Entries inside each section should be ordered by type:
 
 # Changelog
 
-## unreleased - YYYY-MM-DD
+## 8.0.0 - 2026-08-04
 
 ### Python API