many fixes and improvements - rework for modules/ and common/

feat(emailer): add Postmark and Resend providers

backend/Modules/Contents/Data/Album.cs

@@ -0,0 +1,11 @@
+using System.ComponentModel.DataAnnotations;
+using Hutopy.Common.Domain;
+
+namespace Hutopy.Modules.Contents.Data;
+
+public class Album : Entity
+{
+    public bool IsDeleted { get; private set; }   // private set → EF updates it
+    [MaxLength(255)] public required string Title { get; set; }
+    public IList<AlbumPhoto> Photos { get; set; } = new List<AlbumPhoto>();
+}

backend/Modules/Contents/Data/AlbumPhoto.cs

@@ -0,0 +1,15 @@
+using System.ComponentModel.DataAnnotations;
+using Hutopy.Common.Domain;
+
+namespace Hutopy.Modules.Contents.Data;
+
+public class AlbumPhoto : Entity
+{
+    public bool IsDeleted { get; private set; } // private set → EF updates it
+    public Guid AlbumId { get; set; }
+    public Album Album { get; init; } = null!;
+    [MaxLength(2048)] public required string OriginalUrl { get; set; }
+    [MaxLength(2048)] public required string ThumbnailUrl { get; set; }
+    [MaxLength(256)] public string? Caption { get; set; }
+    public int Order { get; set; }
+}

backend/Modules/Contents/Data/ContentsDbContext.cs

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+namespace Hutopy.Modules.Contents.Data;
+
+public class ContentsDbContext(
+    DbContextOptions<ContentsDbContext> options)
+    : DbContext(options)
+{
+    public const string SchemaName = "Content";
+
+    public DbSet<Album> Albums => Set<Album>();
+    public DbSet<AlbumPhoto> AlbumPhotos => Set<AlbumPhoto>();
+
+    protected override void OnModelCreating(
+        ModelBuilder modelBuilder)
+    {
+        modelBuilder.HasDefaultSchema(SchemaName);
+
+        // Album configuration
+        modelBuilder
+            .Entity<Album>()
+            .Property(c => c.CreatedAt)
+            .ValueGeneratedOnAdd()
+            .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+        modelBuilder
+            .Entity<Album>()
+            .Property(c => c.IsDeleted)
+            .HasComputedColumnSql("\"DeletedAt\" IS NOT NULL", stored: true);
+
+        modelBuilder
+            .Entity<Album>()
+            .HasQueryFilter(a => !a.IsDeleted);
+
+        // AlbumPhoto configuration
+        modelBuilder
+            .Entity<AlbumPhoto>()
+            .Property(c => c.CreatedAt)
+            .ValueGeneratedOnAdd()
+            .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+        modelBuilder
+            .Entity<AlbumPhoto>()
+            .Property(c => c.IsDeleted)
+            .HasComputedColumnSql("\"DeletedAt\" IS NOT NULL", stored: true);
+
+        modelBuilder
+            .Entity<AlbumPhoto>()
+            .HasOne(ap => ap.Album)
+            .WithMany(a => a.Photos)
+            .HasForeignKey(ap => ap.AlbumId)
+            .IsRequired();
+
+        modelBuilder
+            .Entity<AlbumPhoto>()
+            .HasQueryFilter(ap => !ap.IsDeleted);
+    }
+}