chore(librarian): onboard to librarian (#374)

Towards googleapis/librarian#2456

Author: parthea

packages/db-dtypes/.github/.OwlBot.lock.yaml

@@ -0,0 +1,10 @@
+image: us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:39628f6e89c9cad27973b9a39a50f7052bec0435ee58c7027b4fa6b655943e31
+libraries:
+  - id: db-dtypes
+    version: 1.4.3
+    apis: []
+    source_roots:
+      - .
+    preserve_regex: []
+    remove_regex: []
+    tag_format: v{version}

packages/db-dtypes/.github/.OwlBot.yaml

@@ -1,5 +1,9 @@
 # Changelog
 
+[PyPI History][1]
+
+[1]: https://pypi.org/project/db-dtypes/#history
+
 ## [1.4.4](https://github.com/googleapis/python-db-dtypes-pandas/compare/v1.4.3...v1.4.4) (2025-09-08)