Convert logic-free classes to records per CLAUDE.md

WebhookEvent, FeatureStateResult, ProjectPermissionRequirement, AuditLog,
Tag, and FeatureUsageDaily are plain data holders with no behavior, so
switch them to records. EF-mapped entities with identity semantics
(User, Organization, Project, Feature, Segment, etc.) stay classes,
since record value-equality and deep ToString fight EF's change tracker.

Also restore `virtual` on AuditService.RecordAsync/LogAsync, which had
been dropped and broke Mock<AuditService>-based test setups.

src/api/MicCheck.Api/Audit/AuditLogQueryService.cs

@@ -6,29 +6,25 @@ namespace MicCheck.Api.Audit;
 
 public class AuditLogQueryService(IMicCheckDbContext db)
 {
-    public async Task<PagedResult<AuditLogResponse>> ListByOrganizationAsync(
-        int organizationId, AuditLogFilter filter, CancellationToken ct = default)
+    public async Task<PagedResult<AuditLogResponse>> ListByOrganizationAsync(int organizationId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.OrganizationId == organizationId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    public async Task<PagedResult<AuditLogResponse>> ListByProjectAsync(
-        int projectId, AuditLogFilter filter, CancellationToken ct = default)
+    public async Task<PagedResult<AuditLogResponse>> ListByProjectAsync(int projectId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.ProjectId == projectId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    public async Task<PagedResult<AuditLogResponse>> ListByEnvironmentAsync(
-        int environmentId, AuditLogFilter filter, CancellationToken ct = default)
+    public async Task<PagedResult<AuditLogResponse>> ListByEnvironmentAsync(int environmentId, AuditLogFilter filter, CancellationToken ct = default)
     {
         var query = db.AuditLogs.Where(l => l.EnvironmentId == environmentId);
         return await ApplyFilterAndPageAsync(query, filter, ct);
     }
 
-    private async Task<PagedResult<AuditLogResponse>> ApplyFilterAndPageAsync(
-        IQueryable<AuditLog> query, AuditLogFilter filter, CancellationToken ct)
+    private async Task<PagedResult<AuditLogResponse>> ApplyFilterAndPageAsync(IQueryable<AuditLog> query, AuditLogFilter filter, CancellationToken ct)
     {
         if (filter.From.HasValue)
             query = query.Where(l => l.CreatedAt >= filter.From.Value);
@@ -66,4 +62,4 @@ public class AuditLogQueryService(IMicCheckDbContext db)
 
         return new PagedResult<AuditLogResponse>(total, items);
     }
-}
+}