feat: Add monitor grouping functionality to backend

- Add optional 'group' field to Monitor schema with trimming and validation
- Add group validation to Joi schemas for create and edit monitor endpoints
- Add GET /api/v1/monitors/team/groups endpoint to fetch unique groups
- Implement case-insensitive group filtering in database layer
- Support for organizing monitors into collapsible groups

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/validation/joi.js

@@ -174,6 +174,7 @@ const createMonitorBodyValidation = joi.object({
 	expectedValue: joi.string().allow(""),
 	matchMethod: joi.string(),
 	gameId: joi.string().allow(""),
+	group: joi.string().max(50).trim().allow(null, "").optional(),
 });
 
 const createMonitorsBodyValidation = joi.array().items(
@@ -203,6 +204,7 @@ const editMonitorBodyValidation = joi.object({
 		usage_temperature: joi.number(),
 	}),
 	gameId: joi.string(),
+	group: joi.string().max(50).trim().allow(null, "").optional(),
 });
 
 const pauseMonitorParamValidation = joi.object({