chore: Prep for 1.11.6 Release (#1351)

## Summary

- Bump version `1.11.5` → `1.11.6` in `__version__.py`
- Set CHANGELOG date to `Mar 10, 2026`
- Add missing CHANGELOG entry for #1343 (constraints were incorrectly
applied when `contract.enforced: false`)

## Checklist

- [x] `CHANGELOG.md` updated with release date
- [x] `dbt/adapters/databricks/__version__.py` bumped to `1.11.6`

Author: sd-db

CHANGELOG.md

@@ -1,4 +1,4 @@
-## dbt-databricks 1.11.6 (TBD)
+## dbt-databricks 1.11.6 (Mar 10, 2026)
 
 ### Features
 
@@ -10,6 +10,7 @@
 
 ### Fixes
 
+- Fix constraints (e.g. primary key, not null) being applied to tables/incrementals/materialized views when `contract.enforced: false` ([#1343](https://github.com/databricks/dbt-databricks/pull/1343))
 - Fix missing `optimize()` call in table v2 materialization path ([#1345](https://github.com/databricks/dbt-databricks/pull/1345))
 - Fix catalog names with special characters (e.g., hyphens) not being quoted in `SHOW SCHEMAS` commands, causing `INVALID_IDENTIFIER` errors ([#1325](https://github.com/databricks/dbt-databricks/issues/1325))
 - Fix liquid clustering rendering on streaming table materialization [#1330](https://github.com/databricks/dbt-databricks/pull/1330)

dbt/adapters/databricks/__version__.py

@@ -1 +1 @@
-version = "1.11.5"
+version = "1.11.6"