Yup I see it. Unfortunately the backtrace isn't particularly revealing:
db:0:kdb.enter.default> bt
Tracing pid 1 tid 100002 td 0xfffffe0012117ac0
kdb_enter() at kdb_enter+0x32/frame 0xfffffe00109b4820
vpanic() at vpanic+0x163/frame 0xfffffe00109b4950
panic() at panic+0x43/frame 0xfffffe00109b49b0
vm_fault() at vm_fault+0x15c5/frame 0xfffffe00109b4ac0
vm_fault_trap() at vm_fault_trap+0xb0/frame 0xfffffe00109b4b10
trap_pfault() at trap_pfault+0x1d9/frame 0xfffffe00109b4b70
calltrap() at calltrap+0x8/frame 0xfffffe00109b4b70
--- trap 0xc, rip = 0xffffffff836cd170, rsp = 0xfffffe00109b4c48, rbp = 0xfffffe00109b4db0 ---
_end() at 0xffffffff836cd170/frame 0xfffffe00109b4db0
sys_reboot() at sys_reboot+0x29c/frame 0xfffffe00109b4e00
amd64_syscall() at amd64_syscall+0x109/frame 0xfffffe00109b4f30
fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe00109b4f30
--- syscall (55, FreeBSD ELF64, reboot), rip = 0x27291a, rsp = 0x820ec2408, rbp = 0x820ec2830 ---
However it looks like it panicked when it tried to make some change after shutdown was initiated:
<118>pfSense is now shutting down ...
<118>
<118>net.inet.carp.allow: 0 -> 0
<6>pflog0: promiscuous mode disabled
Trying to mount root from ufs:/dev/ufsid/65b7583531b4716a [rw,noatime]...
panic: vm_fault_lookup: fault on nofault entry, addr: 0xffffffff836cd000
cpuid = 2
time = 1706519642
KDB: enter: panic
Unclear why it did that but it you clear the crash report and reboot and it doesn't do that every time it's likely a quirk of having just run the initial setup.
You are still running 2.7.1. You should upgrade to 2.7.2 when you can.
Steve