fix(generator/client): append unit to gRPC/HTTP2 transport timeouts

[stupidloud]

Summary

• idle_timeout and ping_timeout on outbound transport (gRPC / HTTP2+TLS) were emitted as bare numeric strings (e.g. "15"), but sing-box parses them as Go time.Duration and rejects values without a unit suffix.
• The server-side generator (generate_server.uc:175-176) and the URLTest generator (generate_client.uc:819) already wrap the same UCI values in strToTime(); this aligns the client outbound transport to behave the same way.

Before: "idle_timeout": "15" → sing-box parse error / field dropped.
After: "idle_timeout": "15s" — matches the sing-box v2ray-transport docs.

Test plan

• Configure a gRPC or HTTP2+TLS outbound with the Idle timeout / Ping timeout fields set in LuCI.
• Verify the generated /var/run/homeproxy/sing-box-c.json contains "idle_timeout": "<N>s" / "ping_timeout": "<N>s" rather than bare numbers.
• Confirm sing-box starts cleanly with the generated config.

[stupidloud]

Reproduction on a live router

Setting Idle timeout / Ping timeout on a gRPC + Reality VLESS node from the LuCI UI and reloading homeproxy produces this in /var/run/homeproxy/homeproxy.log:

2026-06-04 13:42:02 [DAEMON] Reloading service...
2026-06-04 13:42:08 [DAEMON] Service stopped.
FATAL  decode config at /var/run/homeproxy/sing-box-c.json:
       outbounds[3].transport.idle_timeout: time: missing unit in duration "10"
2026-06-04 13:42:09 [DAEMON] Error: wrong client configuration detected.

sing-box refuses to start because outbounds[].transport.idle_timeout is "10" instead of "10s".

CLI workaround until this lands (bypasses the LuCI uinteger validator):

uci set homeproxy.<node>.http_idle_timeout='10s'
uci set homeproxy.<node>.http_ping_timeout='5s'
uci commit homeproxy
/etc/init.d/homeproxy reload

With the patch applied, the numeric UI value (e.g. 10) is routed through strToTime() and the generated JSON contains "idle_timeout": "10s" — sing-box starts cleanly.

[stupidloud]

这个东西就是，singbox/xtls要求grpc的idle和ping有时间单位，通常是s
而原版generate_client.uc只是原值传递

如果不改，这里就要输入带单位的值

但是因为ui类型检查，又无法保存

所以给你 generate_client.uc 补上了时间单位