feat(providers): rebrand CTok to ETok across presets, icons, and docs

The vendor renamed its domain, API endpoints, and trademark from CTok to
ETok. Update all user-facing branding accordingly:

- Presets (claude, claude-desktop, codex, gemini, hermes, openclaw,
  opencode): ctok.ai -> etok.ai, api.ctok.ai -> api.etok.ai, internal
  provider id ctok -> etok, display name CTok.ai -> ETok.ai
- Icons: replace inline placeholder SVG with the new ETok brand PNG,
  moved from `icons` to `iconUrls`; key ctok -> etok; banner logo
  ctok.png -> etok.png
- README (en/zh/ja/de) partner banner: new logo, links, and copy
- i18n (en/ja/zh/zh-TW): partnerPromotion key ctok -> etok

Keep "ctok" in the Codex history-migration whitelist as a legacy id and
add "etok", so existing users' local session history stays correctly
bucketed after the rename.

src-tauri/src/codex_history_migration.rs

@@ -67,6 +67,7 @@ const CC_SWITCH_LEGACY_CODEX_MODEL_PROVIDER_IDS: &[&str] = &[
     "dmxapi",
     "doubaoseed",
     "eflowcode",
+    "etok",
     "kimi",
     "lemondata",
     "longcat",