Add macOS app icon and bundle workflow

.cargo/config.toml

@@ -0,0 +1,2 @@
+[alias]
+bundle-macos = "packager --release --packages ironstorage-desktop --formats app"

README.md

@@ -116,6 +116,18 @@ cargo build --package ironstorage-desktop
 cargo build --package ironstorage-desktop --release
 ```
 
+On macOS, install `cargo-packager` once, then build an application bundle or
+install the release bundle directly into `~/Applications`:
+
+```sh
+cargo install cargo-packager --locked
+cargo bundle-macos
+cargo bundle-macos --out-dir "$HOME/Applications"
+```
+
+The first bundle command writes `target/release/IronStorage.app`. The install
+form replaces `~/Applications/IronStorage.app` with the freshly built bundle.
+
 Build only the shared storage library or the Rust Apple bridge:
 
 ```sh

apps/desktop/Cargo.toml

@@ -6,6 +6,16 @@ edition.workspace = true
 rust-version.workspace = true
 publish = false
 
+[package.metadata.packager]
+product-name = "IronStorage"
+identifier = "de.rfc1437.ironstorage"
+category = "utility"
+icons = ["../../assets/icon-candidates/vault-classic@2x.png"]
+before-packaging-command = { script = "cargo build --release --package ironstorage-desktop", dir = "../.." }
+
+[package.metadata.packager.macos]
+signing-identity = "-"
+
 [[bin]]
 name = "ironstorage-desktop"
 path = "src/main.rs"