feat(fallbacks): add per-rule dest override

Operators can now type an explicit dest (e.g. "8443", "127.0.0.1:8443",
"/dev/shm/x.sock") on each fallback row to override the auto-resolved
child listen+port. Empty keeps the existing auto behavior.

Adds the column to inbound_fallbacks (GORM AutoMigrate), threads it
through the panel form, API docs, and translations.

frontend/src/pages/api-docs/endpoints.ts

@@ -199,12 +199,12 @@ export const sections: readonly Section[] = [
       {
         method: 'GET',
         path: '/panel/api/inbounds/:id/fallbacks',
-        summary: 'List the fallback rules attached to a master VLESS/Trojan TCP-TLS inbound. Each rule links one child inbound (the dest) to optional SNI/ALPN/path/xver match criteria.',
+        summary: 'List the fallback rules attached to a master VLESS/Trojan TCP-TLS inbound. Each rule links one child inbound (the dest) to optional SNI/ALPN/path/dest/xver match criteria. When dest is empty the child inbound\'s listen+port is used.',
         params: [
           { name: 'id', in: 'path', type: 'number', desc: 'Master inbound ID.' },
         ],
         response:
-          '{\n  "success": true,\n  "obj": [\n    {\n      "id": 1,\n      "masterId": 10,\n      "childId": 11,\n      "name": "",\n      "alpn": "",\n      "path": "/vlws",\n      "xver": 2,\n      "sortOrder": 0\n    }\n  ]\n}',
+          '{\n  "success": true,\n  "obj": [\n    {\n      "id": 1,\n      "masterId": 10,\n      "childId": 11,\n      "name": "",\n      "alpn": "",\n      "path": "/vlws",\n      "dest": "",\n      "xver": 2,\n      "sortOrder": 0\n    }\n  ]\n}',
       },
       {
         method: 'POST',
@@ -212,9 +212,9 @@ export const sections: readonly Section[] = [
         summary: 'Replace the entire fallback list for a master inbound. Body is JSON. Triggers an Xray restart.',
         params: [
           { name: 'id', in: 'path', type: 'number', desc: 'Master inbound ID.' },
-          { name: 'fallbacks', in: 'body (json)', type: 'object[]', desc: 'Array of {childId, name, alpn, path, xver, sortOrder} entries.' },
+          { name: 'fallbacks', in: 'body (json)', type: 'object[]', desc: 'Array of {childId, name, alpn, path, dest, xver, sortOrder} entries. Leave dest empty to auto-resolve from the child inbound\'s listen+port; set it (e.g. "8443", "127.0.0.1:8443", "/dev/shm/x.sock") to override.' },
         ],
-        body: '{\n  "fallbacks": [\n    { "childId": 11, "path": "/vlws", "xver": 2 },\n    { "childId": 12, "alpn": "h2" }\n  ]\n}',
+        body: '{\n  "fallbacks": [\n    { "childId": 11, "path": "/vlws", "xver": 2 },\n    { "childId": 12, "alpn": "h2", "dest": "8443" }\n  ]\n}',
         response: '{\n  "success": true,\n  "msg": "Inbound updated"\n}',
       },
     ],

frontend/src/pages/inbounds/InboundFormModal.tsx

@@ -365,13 +365,21 @@ export default function InboundFormModal({
       return;
     }
     setFallbacks(
-      (msg.obj as { childId: number; name?: string; alpn?: string; path?: string; xver?: number }[])
+      (msg.obj as {
+        childId: number;
+        name?: string;
+        alpn?: string;
+        path?: string;
+        dest?: string;
+        xver?: number;
+      }[])
         .map((r) => ({
           rowKey: `fb-${++fallbackKeyRef.current}`,
           childId: r.childId,
           name: r.name || '',
           alpn: r.alpn || '',
           path: r.path || '',
+          dest: r.dest || '',
           xver: r.xver || 0,
         })),
     );
@@ -385,6 +393,7 @@ export default function InboundFormModal({
         name: c.name,
         alpn: c.alpn,
         path: c.path,
+        dest: c.dest,
         xver: Number(c.xver) || 0,
         sortOrder: i,
       })),
@@ -437,6 +446,7 @@ export default function InboundFormModal({
       name: '',
       alpn: '',
       path: '',
+      dest: '',
       xver: 0,
     }]);
   };
@@ -445,11 +455,11 @@ export default function InboundFormModal({
     setFallbacks((prev) => prev.map((r) => {
       if (r.rowKey !== rowKey) return r;
       // When the picker selects a new child inbound and the row hasn't
-      // been hand-edited yet (sni/alpn/path all blank, xver = 0), pull
-      // the SNI/ALPN/Path defaults off that child. Operators who
+      // been hand-edited yet (sni/alpn/path/dest all blank, xver = 0),
+      // pull the SNI/ALPN/Path defaults off that child. Operators who
       // intentionally typed values keep them — we only fill the empties.
       if (typeof patch.childId === 'number' && patch.childId !== r.childId) {
-        const isPristine = !r.name && !r.alpn && !r.path && r.xver === 0;
+        const isPristine = !r.name && !r.alpn && !r.path && !r.dest && r.xver === 0;
         if (isPristine) return { ...r, ...patch, ...deriveFallbackDefaults(patch.childId) };
       }
       return { ...r, ...patch };
@@ -490,6 +500,7 @@ export default function InboundFormModal({
             name: derived.name ?? '',
             alpn: derived.alpn ?? '',
             path: derived.path ?? '',
+            dest: '',
             xver: derived.xver ?? 0,
           };
         });
@@ -1079,6 +1090,12 @@ export default function InboundFormModal({
               value={record.path}
               onChange={(e) => updateFallback(record.rowKey, { path: e.target.value })}
             />
+            <InputAddon>Dest</InputAddon>
+            <Input
+              placeholder={t('pages.inbounds.fallbacks.destPlaceholder') || 'auto'}
+              value={record.dest}
+              onChange={(e) => updateFallback(record.rowKey, { dest: e.target.value })}
+            />
             <InputAddon>xver</InputAddon>
             <InputNumber
               min={0}

frontend/src/schemas/forms/inbound-form.ts

@@ -78,6 +78,7 @@ export const FallbackRowSchema = z.object({
   name: z.string().default(''),
   alpn: z.string().default(''),
   path: z.string().default(''),
+  dest: z.string().default(''),
   xver: z.number().int().min(0).max(2).default(0),
 });
 export type FallbackRow = z.infer<typeof FallbackRowSchema>;