Add NoteService to handle note operations

NoteService should be the only class with access to NoteDao;
nowhere else should NoteDao be accessed directly.

Channel dependencies are static in PacketProcessor, for now.
Ideally they would be injected in the constructor,
but since the constructor is private and I don't want to open
up that can of worms, I'll leave it like this.
At the very least, now we have a way of injecting services into
the handlers. This will make further restructuring way easier.

src/main/java/net/ChannelDependencies.java

@@ -0,0 +1,12 @@
+package net;
+
+import service.NoteService;
+
+import java.util.Objects;
+
+public record ChannelDependencies(NoteService noteService) {
+
+    public ChannelDependencies {
+        Objects.requireNonNull(noteService);
+    }
+}