fix: disk alert escalation compares operands in the wrong order

[CaptainVirgil]

Summary

In bin/core/src/monitor/alert/server.rs, the disk-alert escalation
check compares its operands in the wrong order relative to the CPU
and memory alert paths in the same file.

• CPU (alert_servers, CPU block): alert.level < health.cpu.level
• Memory (same fn, memory block): alert.level < health.mem.level
• Disk (same fn, disk block): health.level < alert.level ← reversed

All three branches carry the identical comment "modify alert level
only if it has increased and not in maintenance", so the disk branch
is inconsistent with its own stated intent, not just with its
siblings.

SeverityLevel derives PartialOrd in declaration order (Ok < Warning < Critical), so the CPU/memory form reads naturally as "is
the freshly observed level higher than what's currently on the open
alert?". With the disk operands swapped, that question becomes
Critical < Warning, Critical < Ok, etc. - comparisons that are
never true once the alert has already opened at Warning or higher.
Practical effect: a disk alert that opens at WARNING and later
crosses into CRITICAL is never updated - it stays reported at
WARNING (or whatever level it first opened at) until it resolves back
to OK and a fresh alert cycle begins.

Fix

Flip the comparison to alert.level < health.level, matching the
CPU and memory branches exactly. One line changed, no behavior
change to the open/close paths.

Testing

• cargo check -p komodo_core passes.
• cargo fmt -p komodo_core -- --check passes (no formatting diff).
• I looked for existing coverage of this escalation logic before
  deciding whether to add a test: there are currently no #[test]
  functions anywhere in the workspace, and alert_servers reads
  live state through db_client()/resource:: helpers with no
  mocking seam in place. Adding a unit test here would mean
  introducing test infrastructure the project doesn't currently have,
  which felt out of scope for a one-line operand fix - happy to add
  one if there's a preferred approach for exercising this path.