Add KI/LLM integration with OpenAI-compatible API support

Features:
- /ai setup - Setup wizard via private chat for security
- /ai status - Show current config (API key masked)
- /ai on/off - Enable/disable AI per chat
- /ai random <1-10> - Set random trigger probability (admins)
- /ai help - Detailed help
- /ask-ai [text] - Generate AI response

Security:
- API keys only entered in private chat
- API keys masked in status display
- Admin-only configuration

Architecture:
- OpenAI-compatible client (OpenAI, Ollama, OpenRouter)
- Global system prompt (.env) + group prompt (DB)
- 50 message context per chat
- SQLite tables: ai_settings, message_context, setup_sessions

Defaults:
- AI disabled by default
- Trigger word: ask-ai
- Random probability: 1%

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ai.ts

@@ -0,0 +1,106 @@
+/**
+ * OpenAI-compatible AI client for multiple providers.
+ * Supports OpenAI, Ollama, OpenRouter, and any OpenAI-compatible API.
+ */
+
+export interface AIConfig {
+  apiKey: string;
+  baseUrl: string;
+  model: string;
+  systemPrompt: string;
+  groupPrompt?: string;
+}
+
+export interface AIMessage {
+  role: 'user' | 'assistant' | 'system';
+  content: string;
+}
+
+/**
+ * Mask an API key for safe display
+ * sk-proj-abc123xyz... → sk-***...***xyz
+ */
+export function maskApiKey(key: string): string {
+  if (!key || key.length < 8) return '***';
+  const start = key.substring(0, 3);
+  const end = key.substring(key.length - 3);
+  return `${start}***...***${end}`;
+}
+
+/**
+ * Generate AI response using OpenAI-compatible API
+ */
+export async function generateAIResponse(
+  config: AIConfig,
+  context: AIMessage[],
+  userMessage: string
+): Promise<string> {
+  const messages: AIMessage[] = [];
+
+  // Build system prompt (global + group)
+  let systemPrompt = config.systemPrompt;
+  if (config.groupPrompt) {
+    systemPrompt += '\n\n' + config.groupPrompt;
+  }
+  messages.push({ role: 'system', content: systemPrompt });
+
+  // Add context messages (last 50)
+  messages.push(...context.slice(-50));
+
+  // Add user message
+  messages.push({ role: 'user', content: userMessage });
+
+  const response = await fetch(`${config.baseUrl}/chat/completions`, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'Authorization': `Bearer ${config.apiKey}`,
+    },
+    body: JSON.stringify({
+      model: config.model,
+      messages,
+      max_tokens: 500,
+      temperature: 0.7,
+    }),
+  });
+
+  if (!response.ok) {
+    const error = await response.text();
+    throw new Error(`AI API error: ${response.status} - ${error}`);
+  }
+
+  const data = await response.json() as { choices: Array<{ message?: { content?: string } }> };
+  return data.choices[0]?.message?.content || 'Keine Antwort erhalten.';
+}
+
+/**
+ * Get default base URL for a provider
+ */
+export function getDefaultBaseUrl(provider: string): string {
+  switch (provider) {
+    case 'openai':
+      return 'https://api.openai.com/v1';
+    case 'ollama':
+      return 'http://localhost:11434/v1';
+    case 'openrouter':
+      return 'https://openrouter.ai/api/v1';
+    default:
+      return 'https://api.openai.com/v1';
+  }
+}
+
+/**
+ * Get available models for a provider
+ */
+export function getProviderModels(provider: string): string[] {
+  switch (provider) {
+    case 'openai':
+      return ['gpt-4o-mini', 'gpt-4o', 'gpt-3.5-turbo'];
+    case 'ollama':
+      return ['llama3', 'llama3.1', 'mistral', 'codellama'];
+    case 'openrouter':
+      return ['openai/gpt-4o-mini', 'anthropic/claude-3.5-sonnet', 'meta-llama/llama-3.1-8b-instruct'];
+    default:
+      return ['gpt-4o-mini'];
+  }
+}