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/test/inbound-form-adapter.test.ts

@@ -6,7 +6,7 @@ import {
   formValuesToWirePayload,
   type RawInboundRow,
 } from '@/lib/xray/inbound-form-adapter';
-import { InboundFormSchema } from '@/schemas/forms/inbound-form';
+import { InboundDbFieldsSchema, InboundFormSchema } from '@/schemas/forms/inbound-form';
 import { SockoptStreamSettingsSchema } from '@/schemas/protocols/stream/sockopt';
 
 // Round-trip: raw DB row → InboundFormValues → wire payload, asserting
@@ -262,3 +262,35 @@ describe('formValuesToWirePayload', () => {
     expect(replay.streamSettings).toEqual(original.streamSettings);
   });
 });
+
+describe('subSortIndex', () => {
+  it('rawInboundToFormValues defaults to 1 when field is absent', () => {
+    const values = rawInboundToFormValues({ ...vlessRow, subSortIndex: undefined });
+    expect(values.subSortIndex).toBe(1);
+  });
+
+  it('rawInboundToFormValues preserves valid values and clamps below-minimum ones to 1', () => {
+    expect(rawInboundToFormValues({ ...vlessRow, subSortIndex: 5 }).subSortIndex).toBe(5);
+    expect(rawInboundToFormValues({ ...vlessRow, subSortIndex: 0 }).subSortIndex).toBe(1);
+    expect(rawInboundToFormValues({ ...vlessRow, subSortIndex: -10 }).subSortIndex).toBe(1);
+  });
+
+  it('formValuesToWirePayload includes subSortIndex in the payload', () => {
+    const values = rawInboundToFormValues({ ...vlessRow, subSortIndex: 3 });
+    const payload = formValuesToWirePayload(values);
+    expect(payload.subSortIndex).toBe(3);
+  });
+
+  it('subSortIndex round-trips through raw → values → payload', () => {
+    const values = rawInboundToFormValues({ ...vlessRow, subSortIndex: 42 });
+    const payload = formValuesToWirePayload(values);
+    const replay = rawInboundToFormValues({ ...vlessRow, subSortIndex: payload.subSortIndex });
+    expect(replay.subSortIndex).toBe(42);
+  });
+
+  it('InboundDbFieldsSchema enforces an integer minimum of 1 and defaults to 1', () => {
+    expect(InboundDbFieldsSchema.partial().safeParse({ subSortIndex: 1.5 }).success).toBe(false);
+    expect(InboundDbFieldsSchema.partial().safeParse({ subSortIndex: 0 }).success).toBe(false);
+    expect(InboundDbFieldsSchema.parse({}).subSortIndex).toBe(1);
+  });
+});