fix: suppress verbose PHP errors and bound login/audit housekeeping cost

- bootstrap.php: disable display_errors/display_startup_errors in favour of
  PHP's own error log, so an uncaught engine error can never leak a stack
  trace or filesystem path to a client.
- LoginRateLimiter: cap tracked address/identity buckets at 20000, evicting
  the least recently active first, so a distributed flood of distinct
  addresses or login names cannot grow login-attempts.json without bound.
- Logger: prune expired audit logs probabilistically (1-in-100) instead of
  on every request, since every request already builds a Logger and a full
  directory scan on each one scales with total rotated log files.

Found during a self-review security audit; full findings available on
request.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

cms/src/NeoCMS/Logger.php

@@ -42,7 +42,9 @@ class Logger
         }
         @chmod($this->logsDir, 0700);
 
-        if ($this->auditEnabled) {
+        // Pruning scans every rotated log file; a Logger is built on every request, so do this
+        // occasionally rather than on each one (the same probabilistic approach as PHP's own session GC).
+        if ($this->auditEnabled && random_int(1, 100) === 1) {
             $this->pruneExpiredLogs();
         }
     }

cms/src/NeoCMS/LoginRateLimiter.php

@@ -16,6 +16,9 @@ final class LoginRateLimiter
     private int $maxIdentityAttempts;
     private int $maxAddressAttempts;
 
+    /** Hard ceiling on tracked buckets, so a distributed flood of distinct addresses or login names cannot grow the state file without bound. */
+    private const MAX_TRACKED_KEYS = 20000;
+
     /** Configure the protected state file and throttling thresholds. */
     public function __construct(string $dataDirectory, array $options = [])
     {
@@ -93,6 +96,16 @@ final class LoginRateLimiter
             }
         }
         unset($record);
+
+        if (count($state) > self::MAX_TRACKED_KEYS) {
+            // Evict the least recently active buckets first; an evicted bucket simply restarts its count.
+            uasort($state, static function (array $a, array $b): int {
+                $lastA = max((int) ($a['locked_until'] ?? 0), $a['attempts'] ? (int) end($a['attempts']) : 0);
+                $lastB = max((int) ($b['locked_until'] ?? 0), $b['attempts'] ? (int) end($b['attempts']) : 0);
+                return $lastA <=> $lastB;
+            });
+            $state = array_slice($state, -self::MAX_TRACKED_KEYS, null, true);
+        }
     }
 
     /** Serialise state updates beneath an exclusive lock to avoid concurrent lost updates. */