feat(usage): add Hermes Agent tracking + fix zero-cost bug + perf

Hermes:
- Parse ~/.hermes/state.db sessions (incl. profiles/*/state.db) into
  proxy_request_logs with data_source='hermes_session', WAL-aware
  incremental sync, Hermes-reported cost preferred over model_pricing
  fallback

Zero-cost bug (dashboard showed \$0 totals):
- GPT-5.5 family default pricing (~83% of affected rows used GPT-5.5)
- find_model_pricing_row: ASCII-lowercase normalization so
  "OpenAI/GPT-5.5@HIGH" matches seeded "gpt-5.5"
- Startup cost backfill in async task: scan rows where total_cost <= 0
  but tokens > 0, recompute via model_pricing in a single transaction

Performance:
- Add (app_type, created_at DESC) covering index for dashboard range
  queries
- Add expression index on COALESCE(data_source, 'proxy') so dedup EXISTS
  subqueries use index lookup instead of full scan; drop superseded
  idx_request_logs_dedup_lookup

Refactor:
- row_to_request_log_detail helper (3-way de-dup; fixes cost_multiplier
  \"1\" vs \"1.0\" drift between callers)
- Promote get_sync_state/update_sync_state to shared session_usage
  module (4 copies -> 1)
- run_step helper in lib.rs replaces 9 if-let-Err blocks
- maybe_backfill_log_costs returns bool to skip duplicate total_cost
  parsing in caller

src/i18n/locales/en.json

@@ -1120,7 +1120,8 @@
       "all": "All",
       "claude": "Claude Code",
       "codex": "Codex",
-      "gemini": "Gemini"
+      "gemini": "Gemini",
+      "hermes": "Hermes"
     },
     "dataSources": "Data Sources",
     "dataSource": {
@@ -1128,7 +1129,8 @@
       "session_log": "Session Log",
       "codex_db": "Codex DB",
       "codex_session": "Codex Session",
-      "gemini_session": "Gemini Session"
+      "gemini_session": "Gemini Session",
+      "hermes_session": "Hermes Session"
     },
     "sessionSync": {
       "trigger": "Sync session logs",

src/i18n/locales/ja.json

@@ -1120,7 +1120,8 @@
       "all": "すべて",
       "claude": "Claude Code",
       "codex": "Codex",
-      "gemini": "Gemini"
+      "gemini": "Gemini",
+      "hermes": "Hermes"
     },
     "dataSources": "データソース",
     "dataSource": {
@@ -1128,7 +1129,8 @@
       "session_log": "セッションログ",
       "codex_db": "Codex DB",
       "codex_session": "Codex セッション",
-      "gemini_session": "Gemini セッション"
+      "gemini_session": "Gemini セッション",
+      "hermes_session": "Hermes セッション"
     },
     "sessionSync": {
       "trigger": "セッションログを同期",

src/i18n/locales/zh.json

@@ -1120,7 +1120,8 @@
       "all": "全部",
       "claude": "Claude Code",
       "codex": "Codex",
-      "gemini": "Gemini"
+      "gemini": "Gemini",
+      "hermes": "Hermes"
     },
     "dataSources": "数据来源",
     "dataSource": {
@@ -1128,7 +1129,8 @@
       "session_log": "会话日志",
       "codex_db": "Codex 数据库",
       "codex_session": "Codex 会话日志",
-      "gemini_session": "Gemini 会话日志"
+      "gemini_session": "Gemini 会话日志",
+      "hermes_session": "Hermes 会话日志"
     },
     "sessionSync": {
       "trigger": "同步会话日志",