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>

database/migrations/2026_11_05_224732_drop_unused_indexes_from_audit_events_table.php

@@ -0,0 +1,31 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * No query filters audit events by level or by resource, so these indexes only cost disk space and write time.
+     */
+    public function up(): void
+    {
+        Schema::table('audit_events', function (Blueprint $table) {
+            if (Schema::hasIndex('audit_events', 'audit_events_level_index')) {
+                $table->dropIndex('audit_events_level_index');
+            }
+            if (Schema::hasIndex('audit_events', ['team_id', 'resource_type', 'resource_uuid', 'created_at'])) {
+                $table->dropIndex(['team_id', 'resource_type', 'resource_uuid', 'created_at']);
+            }
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('audit_events', function (Blueprint $table) {
+            $table->index('level');
+            $table->index(['team_id', 'resource_type', 'resource_uuid', 'created_at']);
+        });
+    }
+};