refactor: merge workspace (core/ + ui/) into a single flat binary crate

integrate CLI into main.rs, no lib.rs by design (YAGNI)

Cargo.toml

@@ -1,8 +1,73 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 # Cargo.toml
 #
-# Workspace manifest for the Noctua project.
+# Noctua COSMIC desktop application
 
-[workspace]
-members = ["core", "ui"]
-resolver = "2"
+[package]
+name = "noctua"
+version = "0.1.0"
+edition = "2021"
+description = "Noctua – a document viewer for the COSMIC™ desktop"
+repository = "https://codeberg.org/wfx/noctua"
+authors = ["Wolfgang Morawetz <wfx@mailbox.org>"]
+license = "GPL-3.0-or-later"
+
+[features]
+default = ["image", "vector", "portable"]
+image = ["dep:image", "dep:kamadak-exif"]
+vector = ["dep:resvg"]
+portable = ["dep:pdfium-render"]
+full = ["image", "vector", "portable"]
+
+[dependencies]
+# Serialization
+serde = { version = "1", features = ["derive"] }
+ron = "0.8"
+
+# Feature-gated document backends
+image = { version = "0.25", optional = true }
+kamadak-exif = { version = "0.5", optional = true }
+pdfium-render = { version = "0.8", optional = true }
+resvg = { version = "0.45", optional = true }
+
+# Logging
+log = "0.4"
+env_logger = "0.11"
+
+# i18n / localization
+i18n-embed = { version = "0.16", features = [
+    "fluent-system",
+    "desktop-requester",
+] }
+i18n-embed-fl = "0.10"
+
+# Resource embedding
+rust-embed = "8"
+
+# Open files/URLs with the system default application
+open = "5"
+
+# Thumbnail cache (freedesktop.org spec)
+dirs = "5.0"
+md5 = "0.7"
+png = "0.17"
+
+# CLI argument parsing
+clap = { version = "4", features = ["derive"] }
+
+# Async runtime (required by libcosmic)
+tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros"] }
+
+[dependencies.libcosmic]
+git = "https://github.com/pop-os/libcosmic.git"
+features = [
+    "a11y",
+    "about",
+    "dbus-config",
+    "multi-window",
+    "single-instance",
+    "tokio",
+    "winit",
+    "wayland",
+    "wgpu",
+]