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-agent/Cargo.toml

@@ -7,7 +7,7 @@ edition = "2021"
 workspace = true
 
 [dependencies]
-compliance-core = { workspace = true }
+compliance-core = { workspace = true, features = ["mongodb"] }
 serde = { workspace = true }
 serde_json = { workspace = true }
 tokio = { workspace = true }