native adblocker using adblock-rust

Summary

Add native request blocking for ads and trackers, with clear per-site controls.

Scope

• Own rule compilation and profile policy in Photon Rust crates.
• Apply blocking before requests through an explicit Photon Engine embedder API.
• Start with a reviewed, licensed filter-list set and bounded background updates.
• Keep the last known-good policy active when an update fails.
• Add per-site pause/allow controls and a bounded element-hiding picker as a later phase.
• Report aggregate blocked counts without retaining request URLs; keep private-session counts in memory only.

Acceptance criteria

• Blocking is verified against controlled Engine fixtures before it is enabled by default.
• Invalid, oversized, or incomplete updates cannot replace the active policy.
• Site exceptions and private-profile behavior are explicit and persisted at the correct profile scope.
• Compilation, downloads, and cache work stay off the UI thread.

Design reference: Zephium separates policy compilation, bounded list updates, cosmetic rules, and site controls: https://github.com/zephium-browser/Zephium/blob/main/docs/adblock.md