fix(sub): {{INBOUND}} = inbound remark, fix {{TRAFFIC_LEFT}} across inbounds (#5443)

Issue 1: the host endpoint remark no longer substitutes the inbound remark
as the config name. {{INBOUND}} always resolves to the inbound's own remark
and {{HOST}} to the host remark, so both can be shown side by side instead
of the host name appearing twice. configName() drops hostRemark entirely;
token help text updated in all locales.

Issue 2: client_traffics.email is globally unique, so a client shared across
several inbounds of one subscription has a single traffic row owned by one
inbound. statsForClient only searched the current inbound's preloaded
ClientStats, missing on every other inbound's link and falling back to
Up=Down=0 -- so {{TRAFFIC_LEFT}} printed the full quota. Build a per-request
email->stats map from all the subscription's inbounds (no extra queries) and
fall back to it.

internal/web/translation/pt-BR.json

@@ -1761,7 +1761,7 @@
           "time": "Tempo e status"
         },
         "descEMAIL": "Email do cliente",
-        "descINBOUND": "Nome da configuração: a observação do host quando definida, caso contrário a observação da entrada",
+        "descINBOUND": "Observação da própria entrada (nome da configuração)",
         "descHOST": "Observação do host",
         "descID": "UUID do cliente",
         "descSHORT_ID": "Primeiros 8 caracteres do UUID",