fix(xhttp): stop injecting scMaxEachPostBytes/scMinPostsIntervalMs defaults (#5141)

The panel seeded xhttp configs with scMaxEachPostBytes=1000000 and
scMinPostsIntervalMs=30 — xray-core''s own defaults — and emitted them
into every generated config and share link. The literal
scMinPostsIntervalMs=30 is a stable DPI fingerprint that Russia''s TSPU
keys on to block connections on mobile networks.

New configs no longer seed these values (empty schema/template defaults,
so xray-core applies its internal defaults). For configs already stored
with the old defaults, the link/subscription builders now drop values
equal to xray-core''s defaults instead of advertising them — covering
panel share links, the raw subscription, and the JSON subscription
without requiring every inbound to be re-saved. Non-default values the
user set deliberately are still emitted.

frontend/src/schemas/protocols/stream/xhttp.ts

@@ -41,7 +41,10 @@ export const XHttpStreamSettingsSchema = z.object({
   seqKey: z.string().default(''),
   uplinkDataPlacement: z.string().default(''),
   uplinkDataKey: z.string().default(''),
-  scMaxEachPostBytes: z.string().default('1000000'),
+  // Empty default on purpose: xray-core already defaults to 1MB/30ms, and
+  // baking the literal values into every config and share link gives DPI a
+  // stable fingerprint (#5141 — TSPU keys on scMinPostsIntervalMs=30).
+  scMaxEachPostBytes: z.string().default(''),
   noSSEHeader: z.boolean().default(false),
   scMaxBufferedPosts: z.number().int().min(0).default(30),
   scStreamUpServerSecs: z.string().default('20-80'),
@@ -51,7 +54,7 @@ export const XHttpStreamSettingsSchema = z.object({
   // Outbound-only fields. Server (inbound) listener ignores these. The
   // panel embeds them in share-link `extra` blobs so the same xhttp
   // config can roundtrip on both sides.
-  scMinPostsIntervalMs: z.string().default('30'),
+  scMinPostsIntervalMs: z.string().default(''),
   uplinkChunkSize: z.number().int().min(0).default(0),
   noGRPCHeader: z.boolean().default(false),
   xmux: XHttpXmuxSchema.optional(),