feat(sub): per-inbound sort order for subscription links

Add a subSortIndex field to inbounds that controls the order of links
in subscription output only: the raw sub body, the HTML sub page, and
the JSON/Clash formats (all served from the same query). Lower values
come first; ties keep id order. The panel inbound list is unaffected.

The value is editable in the inbound form next to the share-address
fields, propagates to nodes via wireInbound, and follows the usual
node-sync rules (copied on import, mirrored while not dirty, never a
structural change).

Rescoped from #5214 by @Ponywka.

frontend/src/generated/zod.ts

@@ -314,6 +314,7 @@ export const InboundSchema = z.object({
   shareAddrStrategy: z.enum(['node', 'listen', 'custom']),
   sniffing: z.unknown(),
   streamSettings: z.unknown(),
+  subSortIndex: z.number().int().min(1),
   tag: z.string(),
   total: z.number().int(),
   trafficReset: z.enum(['never', 'hourly', 'daily', 'weekly', 'monthly']),