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-core/src/error.rs

@@ -3,8 +3,13 @@ use thiserror::Error;
 #[derive(Error, Debug)]
 pub enum CoreError {
     #[error("Database error: {0}")]
+    #[cfg(feature = "mongodb")]
     Database(#[from] mongodb::error::Error),
 
+    #[error("Database error: {0}")]
+    #[cfg(not(feature = "mongodb"))]
+    Database(String),
+
     #[error("Serialization error: {0}")]
     Serialization(#[from] serde_json::Error),