Add ItemDuplicationAnalyser

Sliding-window heuristic over (Steam ID, item code) groups: any window of
THRESHOLD_WINDOW_SECONDS containing THRESHOLD_COUNT or more positive-delta
events for the same player/item pair triggers a Problem. Negative deltas
(drops, transfers out) are filtered. Five events in ten seconds (defaults)
encodes the rule of thumb that legitimate gameplay rarely produces five
identical items in that span.

Constants live as class constants on the analyser so operators can
override via subclass without touching analysis logic; the docblocks
record the justification.

Synthetic fixture extended with a 6-event burst (AdminUser +
Base.Bullets9mm in <1s) and a 4-event sub-threshold group (Player1 +
Base.Plank scattered over 4 minutes) to exercise both paths.

src/Log/ProjectZomboid/ProjectZomboidItemLog.php

@@ -3,7 +3,7 @@
 namespace IndifferentKetchup\Codex\Log\ProjectZomboid;
 
 use IndifferentKetchup\Codex\Analyser\AnalyserInterface;
-use IndifferentKetchup\Codex\Analyser\PatternAnalyser;
+use IndifferentKetchup\Codex\Analyser\ProjectZomboid\ItemDuplicationAnalyser;
 use IndifferentKetchup\Codex\Detective\FilenameDetector;
 use IndifferentKetchup\Codex\Detective\WeightedSinglePatternDetector;
 use IndifferentKetchup\Codex\Parser\ParserInterface;
@@ -22,7 +22,7 @@ class ProjectZomboidItemLog extends ProjectZomboidEventLog
 
     public static function getDefaultAnalyser(): AnalyserInterface
     {
-        return new PatternAnalyser();
+        return new ItemDuplicationAnalyser();
     }
 
     public static function getDetectors(): array