Revert to 'az neon postgres X' structure to match AAZ repository

- Move all commands back under postgres subdirectory
- Create postgres command group and __init__.py files
- Update imports to use postgres module structure
- This aligns with the AAZ repository structure and should resolve validation errors
- Commands are now: az neon postgres branch, az neon postgres project, etc.
- This is a temporary step to get the extension working with AAZ validation

The unified structure (az neon X) will be implemented in a coordinated way
across both AAZ and extension repositories in a future update.

Author: Bhargavsaichinni

src/neon/azext_neon/aaz/latest/neon/__init__.py

@@ -9,11 +9,4 @@
 # flake8: noqa
 
 from .__cmd_group import *
-from ._create import *
-from . import branch
-from . import compute
-from . import endpoint
-from . import neon_database
-from . import neon_role
-from . import organization
-from . import project
+from . import postgres

src/neon/azext_neon/aaz/latest/neon/postgres/__cmd_group.py

@@ -0,0 +1,23 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+#
+# Code generated by aaz-dev-tools
+# --------------------------------------------------------------------------------------------
+
+# pylint: skip-file
+# flake8: noqa
+
+from azure.cli.core.aaz import *
+
+
+@register_command_group(
+    "neon postgres",
+)
+class __CMDGroup(AAZCommandGroup):
+    """Manage Neon Serverless Postgres resources including organizations, projects, and branches.
+    """
+    pass
+
+
+__all__ = ["__CMDGroup"]

src/neon/azext_neon/aaz/latest/neon/postgres/__init__.py

@@ -0,0 +1,19 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+#
+# Code generated by aaz-dev-tools
+# --------------------------------------------------------------------------------------------
+
+# pylint: skip-file
+# flake8: noqa
+
+from .__cmd_group import *
+from ._create import *
+from . import branch
+from . import compute
+from . import endpoint
+from . import neon_database
+from . import neon_role
+from . import organization
+from . import project