Haze 2.0: A Pluggable Visual Effects Engine

Haze 2.0-alpha01 refactors the Compose backdrop blur library into a pluggable visual effects engine. Blur is extracted into a separate `haze-blur` module, while the core now provides a general `VisualEffect` interface for coordinate calculation, layer management, and rendering infrastructure. This enables custom effects like gradient overlays or custom shaders without touching blur internals. The release also fixes blur misalignment in Android split-window scenarios, eliminates per-frame allocations, and promotes the Materials API to stable. Migration requires adding the `haze-blur` dependency and wrapping blur properties inside a `blurEffect {}` block.