feat(ui): utilities, theming, and i18n updates (slice 2/3 of dashboard-v2) (#41500)

* feat(ui): add utilities, theming, and i18n updates (slice 2 of dashboard-v2)

UI utilities and theming improvements extracted from dashboard-v2-structure:

Icons & formatting:
- icons.ts: expanded icon set for new dashboard views
- format.ts: date/number formatting helpers
- tool-labels.ts: human-readable tool name mappings

Theming:
- theme.ts: enhanced theme resolution and system theme support
- theme-transition.ts: simplified transition logic
- storage.ts: theme parsing improvements for settings persistence

Navigation & types:
- navigation.ts: extended tab definitions for dashboard-v2
- app-view-state.ts: expanded view state management
- types.ts: new type definitions (HealthSummary, ModelCatalogEntry, etc.)

Components:
- components/dashboard-header.ts: reusable header component

i18n:
- Updated en, pt-BR, zh-CN, zh-TW locales with new dashboard strings

All changes are additive or backwards-compatible. Build passes.
Part of #36853.

* ui: fix theme and locale review regressions

* ui: fix review follow-ups for dashboard tabs

* ui: allowlist locale password placeholder false positives

* ui: fix theme mode and locale regressions

* Vincentkoc code/pr 41500 route fix (#43829)

* UI: keep unfinished settings routes hidden

* UI: normalize light theme data token

* UI: restore cron type compatibility

---------

Co-authored-by: Vincent Koc <vincentkoc@ieee.org>

.secrets.baseline

@@ -12991,7 +12991,7 @@
         "filename": "ui/src/i18n/locales/en.ts",
         "hashed_secret": "de0ff6b974d6910aca8d6b830e1b761f076d8fe6",
         "is_verified": false,
-        "line_number": 61
+        "line_number": 74
       }
     ],
     "ui/src/i18n/locales/pt-BR.ts": [
@@ -13000,7 +13000,7 @@
         "filename": "ui/src/i18n/locales/pt-BR.ts",
         "hashed_secret": "ef7b6f95faca2d7d3a5aa5a6434c89530c6dd243",
         "is_verified": false,
-        "line_number": 61
+        "line_number": 73
       }
     ],
     "vendor/a2ui/README.md": [