v1.2.0: Fix app icons and DockTilePlugin rename

- Rename WarpDockTilePlugin to GalaxyDockTilePlugin
- Fix runtime icon switching to load from compiled-in assets
- Add NSDockTilePlugIn key to embedded Info.plist
- Replace all channel icons with padded Galaxy variants
- Update build.rs references for renamed plugin
- No longer requires post-bundle steps for icon switching
- Bump version to 1.2.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/DockTilePlugin/GalaxyDockTilePlugin.h

@@ -0,0 +1,12 @@
+#import <Cocoa/Cocoa.h>
+#import <Foundation/Foundation.h>
+
+@interface GalaxyDockTilePlugIn : NSObject <NSDockTilePlugIn>
+{
+    id iconChangedObserver;
+    id defaultsObserver;
+}
+
+@property(strong) id iconChangedObserver;
+@property(strong) id defaultsObserver;
+@end