Remove Warp cloud features and OpenTelemetry

Settings cleanup:
- Remove billing_and_usage, main_page, referrals_page, show_blocks_view,
  environments_page, handoff_environment_creation_modal,
  custom_inference_modal, remove_custom_endpoint_confirmation_dialog,
  transfer_ownership_confirmation_modal, delete_environment_confirmation_dialog
- Remove SettingsSection variants: Account, BillingAndUsage, Referrals,
  SharedBlocks, CloudEnvironments, OzCloudAPIKeys
- Remove SettingsPageViewHandle variants: Main, BillingAndUsage, Referrals,
  CloudEnvironments, OzCloudAPIKeys, SharedBlocks
- Add Platform variant for PlatformPageView
- Gut custom inference endpoint UI from ai_page.rs
- Gut transfer ownership modal from teams_page.rs
- Stub environment_management_pane as dead code
- Remove create_discount_badge usage
- Remove handle_experiment_change call

OpenTelemetry removal:
- Remove opentelemetry, opentelemetry-http, opentelemetry-otlp,
  opentelemetry_sdk, tracing-opentelemetry dependencies
- Replace tracing module with no-op stub
- Delete native.rs and cloud_agent_auth.rs

Bug fixes (prior work):
- Fix apply_diffs() to use markdown_unescaped(ctx)
- Fix notebook executor AIDocumentId handling
- Fix margin/corner-radius consistency in requested_command.rs
- Add document tool handlers to extract_tool_result_content()
- Fix deprecated from_byte_stream in MCP SSE transport
- Fix Cargo.toml profile package spec
- Upgrade rust-toolchain to 1.94.1

app/Cargo.toml

@@ -321,13 +321,8 @@ http_server.workspace = true
 hyper.workspace = true
 libsqlite3-sys = { version = "0.33.0", features = ["bundled"] }
 mio = { version = "1.1.1", features = ["os-poll", "os-ext"] }
-opentelemetry.workspace = true
-opentelemetry-http.workspace = true
-opentelemetry-otlp.workspace = true
-opentelemetry_sdk.workspace = true
 tokio.workspace = true
 tokio-util.workspace = true
-tracing-opentelemetry.workspace = true
 tracing-subscriber.workspace = true
 
 # AWS SDK (loading credentials for BYO LLM)