feat(ai-chat): explicit chatApiStyle selector to surface reasoning (#175)

Rebuilt on develop (after #176) and reworked per review: instead of inferring the
provider from baseUrl (`if (baseUrl)`), the admin picks the chat provider
EXPLICITLY via a new `chatApiStyle` ('openai-compatible' | 'openai'), mirroring
the existing sttApiStyle. A custom baseURL can front real OpenAI too, so the
heuristic was fragile.

Why reasoning was missing: glm-5.2 (and DeepSeek etc.) stream their thinking as
`reasoning_content`, but the official @ai-sdk/openai provider does not map that
field. 'openai-compatible' uses @ai-sdk/openai-compatible, which does — so
reasoning parts now stream (verified live: reasoning-start/delta/end appear, and
disappear when set to 'openai').

- Default (unset) = 'openai-compatible', so existing openai+baseUrl workspaces
  surface reasoning with no admin action. No DB migration (field lives in the
  settings.ai.provider JSON blob).
- includeUsage: true on the openai-compatible model — without it the provider
  omits streamed usage, zeroing the live token counter / reasoning-token
  metadata. The official provider always sent it; this keeps parity. (Confirmed
  live: usage.totalTokens present.)
- openai-compatible has no default endpoint, so with no baseURL (real OpenAI, or
  a role's cross-driver override that cleared it) it falls back to the official
  provider.

Plumbing: ai.types (ChatApiStyle / CHAT_API_STYLES + AiProviderSettings /
MaskedAiSettings), update DTO (@IsIn), ai-settings.service (resolve / getMasked /
update allowlist), workspace.repo updateAiProviderSettings ALLOWED (the second,
SQL-level allowlist the review missed — without it the field never persisted),
ai.service selector. Client: ai-settings-service types + a Protocol <Select> in
the chat section + i18n (en/ru). Scope is chat-only (embeddings don't stream
reasoning; STT already has sttApiStyle).

Tests: ai.service.spec — 4 cases (openai-compatible+baseURL, openai+baseURL,
default-unset, openai-compatible-without-baseURL fallback). Verified on the stand:
default streams reasoning + usage; 'openai' drops reasoning; the setting
round-trips. server + client tsc clean; 36 ai/settings specs green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/public/locales/ru-RU/translation.json

@@ -1160,5 +1160,9 @@
   "Render the full nested tree of all descendant pages": "Показать полное вложенное дерево всех дочерних страниц",
   "Showing {{count}} subpages_one": "Показано {{count}} подстраница",
   "Showing {{count}} subpages_few": "Показано {{count}} подстраницы",
-  "Showing {{count}} subpages_many": "Показано {{count}} подстраниц"
+  "Showing {{count}} subpages_many": "Показано {{count}} подстраниц",
+  "Protocol": "Протокол",
+  "How chat requests are sent and how reasoning is surfaced": "Как отправляются запросы чата и как показывается reasoning",
+  "OpenAI-compatible (surfaces reasoning)": "OpenAI-совместимый (показывает reasoning)",
+  "OpenAI (official)": "OpenAI (официальный)"
 }