Add SearXNG web search for current information

- Add searxng.py service for web queries via SearXNG API
- Integrate search into ai_chat.py with AI-driven search decisions
- AI determines if query needs current info, then searches automatically
- Add SEARXNG_URL, SEARXNG_ENABLED, SEARXNG_MAX_RESULTS config options
- Update documentation in README.md, CLAUDE.md, and .env.example

CLAUDE.md

@@ -39,11 +39,21 @@ Cogs are auto-loaded by `bot.py` from the `cogs/` directory.
 ### Configuration
 All config flows through `config.py` using pydantic-settings. The `settings` singleton is created at module load, so env vars must be set before importing.
 
+### Web Search
+The bot can search the web for current information via SearXNG:
+- `services/searxng.py` provides `SearXNGService` for web queries
+- `ai_chat.py` uses a two-step approach: first asks AI if search is needed, then provides results as context
+- Search is triggered automatically when the AI determines the query needs current information
+- Configured via `SEARXNG_URL`, `SEARXNG_ENABLED`, and `SEARXNG_MAX_RESULTS` env vars
+
 ### Key Design Decisions
 - `ConversationManager` stores per-user chat history in memory with configurable max length
 - Long AI responses are split via `split_message()` in `ai_chat.py` to respect Discord's 2000 char limit
 - The bot responds only to @mentions via `on_message` listener
+- Web search uses AI to decide when to search, avoiding unnecessary API calls for general knowledge questions
 
 ## Environment Variables
 
 Required: `DISCORD_TOKEN`, plus one of `OPENAI_API_KEY`, `OPENROUTER_API_KEY`, `ANTHROPIC_API_KEY`, or `GEMINI_API_KEY` depending on `AI_PROVIDER` setting.
+
+Optional: `SEARXNG_URL` for web search capability.