fix(reports): separate readable categories from report content

Store readable category snapshots separately from details and evidence, validate report categories, and preserve context in admin displays and moderation actions. Widen report categories to TEXT and bump the schema to 3.2.0 without legacy data conversion.

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

src/Core/DBMigratorPart2.php

@@ -269,7 +269,7 @@ trait DBMigratorPart2 {
             target_type VARCHAR(20) NOT NULL,
             target_id BIGINT UNSIGNED NOT NULL,
             reason TEXT NOT NULL,
-            category VARCHAR(40) NOT NULL DEFAULT '',
+            category TEXT NOT NULL,
             status VARCHAR(20) NOT NULL DEFAULT 'pending',
             created_at DATETIME NOT NULL,
             updated_at DATETIME DEFAULT NULL,