chore(usage): drop Hermes Agent tracking integration

Hermes aggregates all in-process API calls into a single sessions row
with the `model` field locked to the initial model, so the usage
dashboard cannot cleanly surface per-call billing context. Two rounds
of UI workarounds (raw mapping, then `<model> @ <host>` display) did
not resolve the user-facing confusion, so the whole tracking
integration is dropped for now.

Removes session_usage_hermes service (and its 17 tests), sync wiring
in commands/usage.rs and lib.rs, _hermes_session/hermes_session
entries in usage_stats SQL (provider_name_coalesce CASE and
effective_usage_log_filter IN clause), frontend Tab/banner/dropdown/
icon entries, and four i18n keys per locale.

Hermes app integration outside usage tracking (proxy routing,
session manager, config) is preserved. Pre-existing hermes rows in
proxy_request_logs are left as orphans — filtered out by the
updated SQL and never surfaced in the UI.

src-tauri/src/lib.rs

@@ -957,10 +957,6 @@ pub fn run() {
                         "Gemini usage initial sync",
                         crate::services::session_usage_gemini::sync_gemini_usage(db),
                     );
-                    run_step(
-                        "Hermes usage initial sync",
-                        crate::services::session_usage_hermes::sync_hermes_usage(db),
-                    );
 
                     // 定期同步
                     let mut interval = tokio::time::interval(std::time::Duration::from_secs(
@@ -981,10 +977,6 @@ pub fn run() {
                             "Gemini usage periodic sync",
                             crate::services::session_usage_gemini::sync_gemini_usage(db),
                         );
-                        run_step(
-                            "Hermes usage periodic sync",
-                            crate::services::session_usage_hermes::sync_hermes_usage(db),
-                        );
                     }
                 });
             });