feat: Implement end-to-end encryption for channels

- Added EncryptionSalt and WrappedRoomKey properties to Channel model.
- Introduced RoomCrypto class for client-side encryption and decryption.
- Updated ChannelService to handle encrypted channels, including creation and rekeying.
- Modified ChannelsController to expose crypto metadata and rekey functionality.
- Enhanced IrcCommandHandler to block joining encrypted channels over IRC.
- Updated database schema with migration for new encryption fields.
- Refactored file validation and image processing services to accommodate encrypted channels.
- Added unit tests for RoomCrypto functionality and updated existing tests for channel services.

src/EchoHub.Server/Data/Migrations/EchoHubDbContextModelSnapshot.cs

@@ -29,6 +29,10 @@ namespace EchoHub.Server.Data.Migrations
                     b.Property<Guid>("CreatedByUserId")
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("EncryptionSalt")
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT");
+
                     b.Property<bool>("IsPublic")
                         .HasColumnType("INTEGER");
 
@@ -45,6 +49,10 @@ namespace EchoHub.Server.Data.Migrations
                         .HasMaxLength(500)
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("WrappedRoomKey")
+                        .HasMaxLength(200)
+                        .HasColumnType("TEXT");
+
                     b.HasKey("Id");
 
                     b.HasIndex("Name")