docs: document ANTHROPIC_API_KEY + GPT/Claude backend switch

Update the two deployment guides to cover the new env vars and the runtime
switch: ANTHROPIC_API_KEY / netrc machine 'anthropic', CONJURER_AI_CONFIG
(gpt|claude), the $gadaj_teraz command, and the note that DALL-E + personal
assistants stay on OpenAI regardless of the switch.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/deployment/DEPLOYMENT_GUIDE.md

@@ -43,11 +43,28 @@ You can rebalance as follows:
 2. Edit each `docker/env/*.env` to replace `HACKME!` with real values:
    - `DISCORD_TOKEN`, `OPENAI_API_KEY`, `CONJURER_API_KEY` (use the same value for
      all services).
+   - `ANTHROPIC_API_KEY` — only if you want the Claude backend (see “AI backend
+     switch” below). Safe to leave unset while running on GPT.
    - For musician/librarian, adjust mounts to the SMB paths you will mount on the
      Pis, e.g. `/mnt/conjurer/music`.
    - Set `CONJURER_CROSSREF_MAILTO` to a real email as required by Crossref.
 3. If you rely on `.netrc`, copy it to `C:\Conjurer\secrets\.netrc` and set
-   `CONJURER_NETRC_FILE` accordingly.
+   `CONJURER_NETRC_FILE` accordingly. The bot reads netrc machines `discord`,
+   `openai`, `anthropic`, `assemblyai`, `spotipy`, `youtube`.
+
+### AI backend switch (GPT ↔ Claude)
+
+The AI chat features run on one backend at a time, selected by a single switch:
+
+- **Startup:** `CONJURER_AI_CONFIG=gpt` (default) or `=claude` in `bot.env`. Unset
+  falls back to the `"active"` key in `system_gpt_settings.json`, then `"gpt"`.
+- **Runtime:** the `$gadaj_teraz <config>` Discord command (Vykidailo only) flips
+  the backend live and persists the choice.
+- The named configs (which provider, which models) live in
+  `system_gpt_settings.json` — add more there. Claude needs `ANTHROPIC_API_KEY`;
+  GPT needs `OPENAI_API_KEY`. Image generation (`imaginuje sobie:`) and personal
+  assistants always use OpenAI regardless of the switch (Anthropic has no
+  equivalent), and degrade quietly if `OPENAI_API_KEY` is absent.
 
 ## 4. Install Docker on Raspberry Pis and Windows