fix: Fix bootloop logging crash (#1357)

## Summary

* **What is the goal of this PR?** On a cold boot (or after a crash that
corrupts RTC RAM), logHead contains garbage. Then addToLogRingBuffer
does: ``strncpy(logMessages[logHead], message, MAX_ENTRY_LEN - 1); ``
With garbage logHead, this computes a completely invalid address. The %
MAX_LOG_LINES guard on line 16 only runs after the bad store, which is
too late. The fix is to clamp logHead before use.

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
  specific areas to focus on).

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### AI Usage

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Did you use AI tools to help write this code? _**NO**_ (did use claude
for the magic hash value)

lib/hal/HalSystem.cpp

@@ -76,6 +76,14 @@ void begin() {
   // `clearPanic()` to clear it after dumping
   if (!isRebootFromPanic()) {
     clearPanic();
+  } else {
+    // Panic reboot: preserve logs and panic info, but clamp logHead in case the
+    // panic occurred before begin() ever ran (e.g. in a static constructor).
+    // If logHead was out of range, logMessages is also garbage — clear it so
+    // getLastLogs() does not dump corrupt data into the crash report.
+    if (sanitizeLogHead()) {
+      clearLastLogs();
+    }
   }
 }