fix(audit): stop duplicate and empty audit rows

- Set env var version and compose parsing version while creating, so a create writes one row
- Record no rows for the auto-created preview copy of an env var
- Record env and application API updates only with the fields that really changed
- Store no change data for new env vars, and null for empty change data
- Store metadata team_id as an integer
- Drop the unused level and resource indexes of audit_events

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/Http/Controllers/Api/DatabasesController.php

@@ -4016,14 +4016,19 @@ class DatabasesController extends Controller
         if ($request->has('comment')) {
             $env->comment = $request->comment;
         }
-        $env->save();
+        // One audit row with the database context, instead of a second row from the model.
+        $env->withoutAuditLogging(fn () => $env->save());
+        $changedFields = auditSavedFields($env);
 
-        auditLog('api.database.env_updated', [
-            'team_id' => $teamId,
-            'database_uuid' => $database->uuid,
-            'env_uuid' => $env->uuid,
-            'env_key' => $env->key,
-        ]);
+        if ($changedFields !== []) {
+            auditLog('api.database.env_updated', [
+                'team_id' => $teamId,
+                'database_uuid' => $database->uuid,
+                'env_uuid' => $env->uuid,
+                'env_key' => $env->key,
+                'changed_fields' => $changedFields,
+            ]);
+        }
 
         return response()->json($this->removeSensitiveEnvData($env))->setStatusCode(201);
     }