chore: add LICENSE, README, CHANGELOG, and publish metadata

Add MIT license, README with usage/install instructions and hotkey
binding examples, CHANGELOG for v0.1.0, and complete Cargo.toml
metadata (repository, homepage, keywords, categories). Remove unused
niri-ipc dependency.

CHANGELOG.md

@@ -0,0 +1,16 @@
+# Changelog
+
+## 0.1.0 (2026-04-07)
+
+Initial release.
+
+### Features
+
+- GPU-rendered ring light overlay using wgpu/WGSL fragment shader
+- Rounded rectangle SDF with gaussian glow falloff
+- Full desktop input passthrough via dynamic `wl_region` cursor hole
+- Cursor avoidance with rounded-square soft fade
+- Color temperature support: presets (warm, cool, studio, daylight, golden) and custom Kelvin
+- Toggle on/off via PID lock file and SIGUSR1 signaling
+- Works on any wlroots-based Wayland compositor (Sway, Hyprland, niri, river, etc.)
+- MangoHUD suppression for clean Vulkan overlay