Fix #2781, guard server-only TIME message ID

[sylvesterkaczmarek]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

Fix #2781.

Guard the SEND_CMD_MID declaration and initialization in CFE_TIME_TaskPipe() with CFE_PLATFORM_TIME_CFG_SERVER.

SEND_CMD_MID is only used by the server-only CFE_TIME_ToneSendCmd() dispatch path. In a TIME client configuration, the previous unconditional declaration and initialization left a server-only static variable unused, which causes strict client builds to fail.

Testing performed

1. Verified the change is limited to the server-only message ID declaration and initialization in modules/time/fsw/src/cfe_time_dispatch.c.
2. Verified the existing server-only use remains under the same CFE_PLATFORM_TIME_CFG_SERVER == true condition.
3. Upstream GitHub Actions are currently awaiting authorization for this fork PR, so no CI result is being claimed yet.

Expected behavior changes

• API Change: none.
• Behavior Change: TIME client builds no longer compile the unused server-only SEND_CMD_MID variable.
• TIME server dispatch behavior is unchanged.

System(s) tested on

• The issue was reported on RHEL 9.x, x86_64, using the native_std build.
• This PR is awaiting NASA GitHub Actions authorization for repository CI validation.

Additional context

The patch intentionally keeps the declaration, initialization, and use of SEND_CMD_MID under the same server-only compile-time condition.

Third party code

None.

Contributor Info - All information REQUIRED for consideration of pull request

Sylvester Kaczmarek, Personal