fix: compose passes .env through env_file; clearer name and channel messages [CI]

podman-compose does not substitute defaults inside "environment:" (a value
like ${MOSHIRO_NAME:-} reached the node as the literal text), so the node was
enrolled with an invalid name and reported the wrong network scope. The three
compose files now read .env with env_file and only interpolate image and
network_mode; the Backend .env keys are the container's own names
(MoShiro__PublicUrl, MoShiro__ClaimCode).

- The generated .env no longer carries a comment line for MOSHIRO_NAME; the
  dialog says how to choose a name instead.
- The container entrypoint prints the name it enrolls with and defaults
  MOSHIRO_NETWORK_SCOPE to host (Docker Desktop sets container in .env).
- The overview and line pages say "measurement channel not established"
  instead of "not connected": the agent can be reachable and pingable while
  the measurement TCP/UDP path is not.

web/display/src/pages/Line.tsx

@@ -278,7 +278,7 @@ export function Line() {
         {line.data ? (
           <div className="row wrap" style={{ marginTop: 12 }}>
             <Dot tone={line.data.online && line.data.probe_connected ? 'ok' : line.data.online ? 'warn' : 'bad'} />
-            <span className="muted">{line.data.online ? (line.data.probe_connected ? '在线' : 'Agent 在线，Probe 未连接') : 'Agent 离线'}</span>
+            <span className="muted">{line.data.online ? (line.data.probe_connected ? '在线' : 'Agent 在线，测量通道未建立（Probe 没能和它建立测量会话；机器可能是通的，ping 通不代表测量用的 TCP 和 UDP 通道可用）') : 'Agent 离线'}</span>
             <span className="row" style={{ gap: 6 }}>
               <span className="faint">Agent</span>
               <NodeTag info={infos.get(line.data.agent_id)} />

web/display/src/pages/Overview.tsx

@@ -102,7 +102,7 @@ function Card({ agent, host, range, infos }: { agent: AgentCard; host: HostItem
                   <span className="name">{l.probe_name}</span>
                   {infos.get(l.probe_id)?.isp_key ? <IspIcon ispKey={infos.get(l.probe_id)!.isp_key!} name={infos.get(l.probe_id)!.isp_name} /> : null}
                 </span>
-                {!l.probe_connected && l.online ? <Chip tone="warn">未连接</Chip> : <span className="faint line-range">{OVERVIEW_RANGES.find((r) => r.value === range)?.label ?? range}</span>}
+                {!l.probe_connected && l.online ? <span title="Agent 在线，但这个 Probe 没能和它建立测量会话（控制通道连不上或握手超时）。机器本身可能是通的、ping 也能通，这里说的是测量用的 TCP 和 UDP 通道，线路或运营商对它们的处理可能和 ping 不一样。"><Chip tone="warn">测量通道未建立</Chip></span> : <span className="faint line-range">{OVERVIEW_RANGES.find((r) => r.value === range)?.label ?? range}</span>}
               </div>
               <LineStrips lineId={l.id} range={range} m={m} />
             </Link>