Add multi-provider AI config safeguards

.env.example

@@ -1,5 +1,32 @@
-PERPLEXITY_API_KEY=your_perplexity_api_key_here
+# Оставьте незакомментированным только один AI API KEY.
+# Если одновременно указать несколько AI ключей, колонка выдаст ошибку.
+AI_PROVIDER=
+
+# Perplexity
+# PERPLEXITY_API_KEY=your_perplexity_api_key_here
 PERPLEXITY_MODEL=llama-3.1-sonar-small-128k-chat
+PERPLEXITY_API_URL=https://api.perplexity.ai/chat/completions
+
+# OpenAI
+# OPENAI_API_KEY=your_openai_api_key_here
+OPENAI_MODEL=gpt-4o-mini
+OPENAI_API_URL=https://api.openai.com/v1/chat/completions
+
+# Gemini
+# GEMINI_API_KEY=your_gemini_api_key_here
+GEMINI_MODEL=gemini-2.5-flash
+GEMINI_API_URL=https://generativelanguage.googleapis.com/v1beta/openai/chat/completions
+
+# Z.ai
+# ZAI_API_KEY=your_zai_api_key_here
+ZAI_MODEL=glm-5
+ZAI_API_URL=https://api.z.ai/api/paas/v4/chat/completions
+
+# Anthropic Claude
+# ANTHROPIC_API_KEY=your_anthropic_api_key_here
+ANTHROPIC_MODEL=claude-sonnet-4-20250514
+ANTHROPIC_API_URL=https://api.anthropic.com/v1/messages
+ANTHROPIC_API_VERSION=2023-06-01
 DEEPGRAM_API_KEY=your_deepgram_api_key_here
 PORCUPINE_ACCESS_KEY=your_porcupine_access_key_here
 PORCUPINE_SENSITIVITY=0.8