fix(xray): reject configs xray-core refuses, and check the fixtures against it

The frontend's golden fixtures are the panel's model of an xray config, but
nothing ever asked xray-core whether it would accept them: the snapshots only
prove the Zod schemas agree with themselves. Building every fixture through the
same config builders the panel hands its config to — conf.InboundDetourConfig
for the full-config and AddInbound paths, conf.RouterConfig for
ApplyRoutingConfig, conf.DNSConfig for the dns section — found seven the core
refuses, three of them reachable from the panel's own UI. A refusal is not
scoped to one inbound: the config fails to load and every inbound stays down.

Hysteria: xray-core builds version 2 only, in both the protocol settings and
the transport settings, but the inbound settings schema accepted any version
from 1 up and its comment claimed upstream still supported v1. Both fixtures
carried version 1. The schema now pins 2, GenXrayInboundConfig heals stored
rows on the way out the way it already heals shadowsocks ciphers and wireguard
peers, and the share link drops the dead hysteria:// scheme — the subscription
server already emitted hysteria2:// for the same inbound.

XHTTP uplinkDataPlacement: both transport forms offered "query", which the core
has never accepted for that field (auto and body always, cookie and header in
packet-up mode). Replaced with auto, which was missing, and the default label
now names auto rather than body.

FinalMask items: switching an item to the rand-driven array kind wrote
packet:[] next to the rand. xray-core counts an empty array as a packet and
every item kind is exclusive, so noise answers "len(item.Packet) > 0 &&
item.Rand.To > 0" and header-custom "exactly one item kind must be set". The
editor now clears the packet, and GetXrayConfig strips the residue from rows
already saved with it.

The remaining four were stale fixtures: an xmc mask still on the usernames
shape v26.7.28 replaced with profiles, a fragment mask with no length, and
header-custom and noise items passing an array to the string packet kind — all
shapes the panel's own editors cannot produce.

golden_fixtures_xray_test.go keeps this from drifting again: every fixture in
every category is built through xray-core on each run, with a self-signed pair
standing in for the deployment certificate paths, so the next core bump reports
which fixture it broke.

internal/web/service/inbound.go

@@ -713,6 +713,52 @@ func stripIncompleteXmcMasks(stream map[string]any) int {
 	return dropped
 }
 
+// dropEmptyRandPackets removes the leftover empty "packet" from finalmask
+// items that also carry a rand, and reports how many it cleared.
+//
+// xray-core treats even an empty array as a packet, and every item kind is
+// exclusive: noise refuses "len(item.Packet) > 0 && item.Rand.To > 0" and
+// header-custom refuses "exactly one item kind must be set". Either error
+// fails the whole config build, so one such item keeps every inbound offline.
+// The panel's mask editor wrote that pair whenever an item was switched to the
+// rand-driven array kind, so stored rows carry it; clearing an empty packet
+// changes nothing about the mask the admin configured.
+func dropEmptyRandPackets(node any) int {
+	switch value := node.(type) {
+	case map[string]any:
+		cleared := 0
+		if packet, ok := value["packet"].([]any); ok && len(packet) == 0 && randIsSet(value["rand"]) {
+			delete(value, "packet")
+			cleared++
+		}
+		for _, child := range value {
+			cleared += dropEmptyRandPackets(child)
+		}
+		return cleared
+	case []any:
+		cleared := 0
+		for _, child := range value {
+			cleared += dropEmptyRandPackets(child)
+		}
+		return cleared
+	default:
+		return 0
+	}
+}
+
+// randIsSet reports whether a finalmask item's rand selects a random packet.
+// It is a number on header-custom items and a dash-range string on noise ones.
+func randIsSet(value any) bool {
+	switch rand := value.(type) {
+	case float64:
+		return rand > 0
+	case string:
+		return rand != "" && rand != "0" && rand != "0-0"
+	default:
+		return false
+	}
+}
+
 // validateFinalMaskXmcProfiles rejects an xmc finalmask without complete
 // profiles at save time, so the admin gets a targeted error instead of a core
 // that refuses to start (or, after GetXrayConfig heals it, an inbound quietly