Implement grower notes CRUD endpoints

[kaohenry9287]

Description

Add backend API endpoints to support the internal staff notes feature for grower profiles
Greenstand/treetracker-admin-client#669

Endpoints needed

Method	Endpoint	Description
GET	/api/{org}/planter/{growerId}/notes	Fetch all notes for a grower
POST	/api/{org}/planter/{growerId}/notes	Create a new note
PATCH	/api/{org}/planter/{growerId}/notes/{noteId}	Edit an existing note
DELETE	/api/{org}/planter/{growerId}/notes/{noteId}	Delete a note

New table grower_note:

Column	Type	Notes
id	serial (primary key)
planter_id	integer	FK → planter.id
content	text
author_id	integer	FK → admin_user.id
author_name	varchar	Denormalized for display
created_at	timestamp
updated_at	timestamp