fix(inbounds): allow negative subSortIndex for subscription order (#6465)

* fix(inbounds): allow negative subSortIndex for subscription order

Preserve explicitly set negative indices so primary inbounds can sort
ahead of the default without renumbering peers; keep 0/omitted → 1.

* fix(inbounds): gofumpt model.go and trim subSortIndex comments

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Co-authored-by: mrchatam <287639636+mrchatam@users.noreply.github.com>

frontend/src/generated/zod.ts

@@ -638,7 +638,7 @@ export const InboundSchema = z.object({
   shareAddrStrategy: z.enum(['node', 'listen', 'custom']),
   sniffing: z.unknown(),
   streamSettings: z.unknown(),
-  subSortIndex: z.number().int().min(1),
+  subSortIndex: z.number().int(),
   tag: z.string(),
   total: z.number().int(),
   trafficReset: z.enum(['never', 'hourly', 'daily', 'weekly', 'monthly']),