fix(maintenance): stop silent deletion of one-time maintenance windows

Maintenance windows could disappear seconds after creation when the API received
a payload with end dates already in the past. The repository auto-set
expiry = end for one-time windows (repeat = 0), and Mongo's TTL index on the
expiry field then deleted the row on its next sweep. This was particularly
visible with automation tools sending payloads in non-UTC timezones.

## Changes

### Validator hardening
- Add .strict() to create + edit body schemas so unknown keys return 400
  instead of being silently dropped.
- Refine end > start on create.
- Refine end > now for one-time create payloads (repeat = 0).
- Refine end > start on edit when both are provided.
- Remove the accepted expiry field from both schemas.

### Stop the auto-delete behaviour
- Repository.create no longer copies end into expiry.
- Schema's expiry field + TTL index removed.
- Migration 0007 drops the live TTL index and unsets stale expiry values on
  existing rows so legacy data is no longer at risk.

### Client
- Form submission no longer includes expiry.

server/src/validation/maintenanceWindowValidation.ts

@@ -7,17 +7,26 @@ const dateToString = z.coerce.date().transform((d) => d.toISOString());
 // Maintenance Window Validations
 //****************************************
 
-export const createMaintenanceWindowBodyValidation = z.object({
-	monitors: z.array(z.string()).min(1, "At least one monitor is required"),
-	name: z.string().min(1, "Name is required"),
-	active: z.boolean().optional(),
-	duration: z.number().min(1, "Duration is required"),
-	durationUnit: z.enum(["seconds", "minutes", "hours", "days"]),
-	start: dateToString,
-	end: dateToString,
-	repeat: z.number().min(0, "Repeat must be a non-negative number"),
-	expiry: dateToString.optional(),
-});
+export const createMaintenanceWindowBodyValidation = z
+	.object({
+		monitors: z.array(z.string()).min(1, "At least one monitor is required"),
+		name: z.string().min(1, "Name is required"),
+		active: z.boolean().optional(),
+		duration: z.number().min(1, "Duration is required"),
+		durationUnit: z.enum(["seconds", "minutes", "hours", "days"]),
+		start: dateToString,
+		end: dateToString,
+		repeat: z.number().min(0, "Repeat must be a non-negative number"),
+	})
+	.strict()
+	.refine((data) => new Date(data.end).getTime() > new Date(data.start).getTime(), {
+		message: "End must be after start",
+		path: ["end"],
+	})
+	.refine((data) => data.repeat > 0 || new Date(data.end).getTime() > Date.now(), {
+		message: "End must be in the future for one-time maintenance windows",
+		path: ["end"],
+	});
 
 export const getMaintenanceWindowByIdParamValidation = z.object({
 	id: z.string().min(1, "ID is required"),
@@ -43,14 +52,19 @@ export const editMaintenanceWindowByIdParamValidation = z.object({
 	id: z.string().min(1, "ID is required"),
 });
 
-export const editMaintenanceByIdWindowBodyValidation = z.object({
-	active: z.boolean().optional(),
-	name: z.string().optional(),
-	repeat: z.number().optional(),
-	start: dateToString.optional(),
-	end: dateToString.optional(),
-	expiry: dateToString.optional(),
-	monitors: z.array(z.string()).optional(),
-	duration: z.number().optional(),
-	durationUnit: z.enum(["seconds", "minutes", "hours", "days"]).optional(),
-});
+export const editMaintenanceByIdWindowBodyValidation = z
+	.object({
+		active: z.boolean().optional(),
+		name: z.string().optional(),
+		repeat: z.number().optional(),
+		start: dateToString.optional(),
+		end: dateToString.optional(),
+		monitors: z.array(z.string()).optional(),
+		duration: z.number().optional(),
+		durationUnit: z.enum(["seconds", "minutes", "hours", "days"]).optional(),
+	})
+	.strict()
+	.refine((data) => !data.start || !data.end || new Date(data.end).getTime() > new Date(data.start).getTime(), {
+		message: "End must be after start",
+		path: ["end"],
+	});