Fix Dialyzer :exact_compare warnings for NaN/infinity checks

Fixes 3 Dialyzer warnings about impossible comparisons when checking for NaN
and infinity values in sensor validation.

Problem:
Dialyzer correctly identified that comparing a float with atoms (:nan,
:infinity, :neg_infinity) using == can never evaluate to true. The previous
code attempted to validate sensor values by comparing with these atoms, which
is incorrect in Erlang/Elixir.

Solution:
Use proper float comparison techniques:
- NaN detection: value != value (NaN is the only value that doesn't equal itself)
- Infinity detection: value > 1.0e308 or value < -1.0e308 (beyond max float range)

This approach correctly identifies special float values without impossible
comparisons that Dialyzer flags.

Dialyzer results:
- Before: Total errors: 509, Skipped: 506
- After: Total errors: 506, Skipped: 506
- Status: done (passed successfully), EXIT CODE: 0

All 3434 tests passing. Validation logic now correctly identifies NaN and
infinity values while satisfying Dialyzer type analysis.

lib/towerops/agent/validator.ex

@@ -369,10 +369,17 @@ defmodule Towerops.Agent.Validator do
 
   # Validate sensor value (must be finite float/int)
   defp validate_sensor_value(value) when is_float(value) or is_integer(value) do
-    if is_float(value) and (value == :nan or value == :infinity or value == :neg_infinity) do
-      {:error, {:invalid_sensor_value, "Sensor value must be finite number"}}
-    else
-      :ok
+    # Check for NaN (NaN is the only value that doesn't equal itself)
+    # Check for infinity by comparing with max/min float values
+    cond do
+      is_float(value) and value != value ->
+        {:error, {:invalid_sensor_value, "Sensor value must be finite number (not NaN)"}}
+
+      is_float(value) and (value > 1.0e308 or value < -1.0e308) ->
+        {:error, {:invalid_sensor_value, "Sensor value must be finite number (not infinity)"}}
+
+      true ->
+        :ok
     end
   end