Remove Slint host — delete host-window.rs and slint_viz.rs

[elasticdotventures]

Summary

With v1.8.0 the visualization layer has been fully rebuilt as arc-kit-au (a native Rust petgraph-backed evidence graph engine), and all business logic has been extracted into host_ops.rs and evidence.rs. The Slint host (host-window.rs, slint_viz.rs) is now fully orphaned with no remaining value.

Action

• Delete crates/ledgerr-host/src/bin/host-window.rs
• Delete crates/ledgerr-host/src/slint_viz.rs (if still present)
• Remove slint dependency from crates/ledgerr-host/Cargo.toml
• Remove slint-host feature flag from workspace Cargo.toml
• Clean up any remaining #[cfg(feature = "slint-host")] references

Verification

• cargo check -p ledgerr-host passes
• cargo check -p ledgerr-tauri passes (on Windows/CI)
• No other crate references deleted Slint modules' exports