Fix dashboard wasm build and feature-gate mongodb for wasm compatibility

- Feature-gate mongodb in compliance-core (optional, default on) so wasm
  builds don't pull in tokio/mio via mongodb
- Use bson v2 directly for ObjectId types (wasm-compatible)
- Restructure dashboard infrastructure/mod.rs: server function modules
  always compiled (for RPC stubs), server-only modules cfg-gated
- Remove reqwest from dashboard web feature (not needed, data flows
  through server functions)
- Add .gitignore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compliance-dashboard/src/lib.rs

@@ -1,8 +1,6 @@
 pub mod app;
 pub mod components;
+pub mod infrastructure;
 pub mod pages;
 
-#[cfg(feature = "server")]
-pub mod infrastructure;
-
 pub use app::App;