feat: chatbot model setting + tool-calling toggle, simplify admin AI config (v0.59.0)

Chatbot (general assistant + per-recipe Q&A) now resolves its default model
from its own site setting (DEFAULT_CHAT_PROVIDER/MODEL) instead of sharing
the generic "text" use case with recipe generation, so admins can point it
at a different model.

Added AI_TOOL_CALLING_ENABLED: turns off the chatbot's createRecipe/
addToShoppingList tools (and the forced-retry pass) for models that don't
reliably support tool calling — it falls back to plain text answers.

Simplified the admin AI Configuration page: it showed provider keys and
routing settings twice (a read-only card, then an identical edit form).
Merged into one editable section; the resolved fallback provider is now a
one-line note instead of its own card.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,15 @@
 
 All notable changes to Epicure are documented here. This file is mirrored in-app at `/changelog` (and in the admin dashboard) via `apps/web/lib/changelog.ts` — update both together.
 
+## 0.59.0 — 2026-07-20 21:15
+
+### Added
+- Admin: chatbot now has its own default-model setting, separate from generic text generation — the general assistant and per-recipe Q&A chat can be pointed at a different model than recipe generation.
+- Admin: tool calling (the chatbot's inline recipe/shopping-list drafting) can be toggled off — useful for a local/Ollama model that doesn't reliably support it, so the bot falls back to plain text answers instead.
+
+### Fixed
+- Simplified the admin AI Configuration page — it showed the same provider keys and routing settings twice (once read-only, once as an edit form). Merged into one section.
+
 ## 0.58.0 — 2026-07-20 21:00
 
 ### Fixed