chore: documentation (#76)

* chore: update docstring example to use python code block

* docs: add documentation

* feat: add docs build + fix other workdlows

* fix: add missing return type

docs/reference/db.md

@@ -0,0 +1,28 @@
+# `db`
+
+Here's the reference for all database session utilities, transaction helpers, and locking functions.
+
+You can import them directly from `fastapi_toolsets.db`:
+
+```python
+from fastapi_toolsets.db import (
+    LockMode,
+    create_db_dependency,
+    create_db_context,
+    get_transaction,
+    lock_tables,
+    wait_for_row_change,
+)
+```
+
+## ::: fastapi_toolsets.db.LockMode
+
+## ::: fastapi_toolsets.db.create_db_dependency
+
+## ::: fastapi_toolsets.db.create_db_context
+
+## ::: fastapi_toolsets.db.get_transaction
+
+## ::: fastapi_toolsets.db.lock_tables
+
+## ::: fastapi_toolsets.db.wait_for_row_change