feat(chat): integrate chat project into monorepo with full app structure

- Restructure chat as apps/mobile, apps/web, apps/landing, backend
- Add NestJS backend for secure Azure OpenAI API calls
- Remove exposed API key from mobile app (security fix)
- Add shared chat-types package
- Create SvelteKit web app scaffold
- Create Astro landing page scaffold
- Update pnpm workspace configuration
- Add project-level CLAUDE.md documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

chat/apps/mobile/scripts/create_usage_functions.sql

@@ -0,0 +1,144 @@
+-- Funktionen zum Abfragen der Token-Nutzung
+
+-- 1. Funktion zum Abrufen der Token-Nutzung eines Benutzers, gruppiert nach Modell
+CREATE OR REPLACE FUNCTION get_user_model_usage(user_id UUID)
+RETURNS TABLE (
+  model_id UUID,
+  model_name TEXT,
+  total_prompt_tokens BIGINT,
+  total_completion_tokens BIGINT,
+  total_tokens BIGINT,
+  total_cost DECIMAL(10, 6)
+)
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+BEGIN
+  RETURN QUERY
+  SELECT 
+    ul.model_id,
+    m.name AS model_name,
+    SUM(ul.prompt_tokens)::BIGINT AS total_prompt_tokens,
+    SUM(ul.completion_tokens)::BIGINT AS total_completion_tokens,
+    SUM(ul.total_tokens)::BIGINT AS total_tokens,
+    SUM(ul.estimated_cost)::DECIMAL(10, 6) AS total_cost
+  FROM 
+    usage_logs ul
+  JOIN
+    models m ON ul.model_id = m.id
+  WHERE 
+    ul.user_id = get_user_model_usage.user_id
+  GROUP BY 
+    ul.model_id, m.name
+  ORDER BY 
+    total_cost DESC;
+END;
+$$;
+
+-- 2. Funktion zum Abrufen der Token-Nutzung eines Benutzers nach Zeitraum
+CREATE OR REPLACE FUNCTION get_user_usage_by_period(user_id UUID, period TEXT)
+RETURNS TABLE (
+  time_period TEXT,
+  total_tokens BIGINT,
+  total_cost DECIMAL(10, 6)
+)
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+BEGIN
+  IF period = 'day' THEN
+    RETURN QUERY
+    SELECT 
+      TO_CHAR(ul.created_at, 'YYYY-MM-DD') AS time_period,
+      SUM(ul.total_tokens)::BIGINT AS total_tokens,
+      SUM(ul.estimated_cost)::DECIMAL(10, 6) AS total_cost
+    FROM 
+      usage_logs ul
+    WHERE 
+      ul.user_id = get_user_usage_by_period.user_id
+    GROUP BY 
+      time_period
+    ORDER BY 
+      time_period DESC;
+  ELSIF period = 'month' THEN
+    RETURN QUERY
+    SELECT 
+      TO_CHAR(ul.created_at, 'YYYY-MM') AS time_period,
+      SUM(ul.total_tokens)::BIGINT AS total_tokens,
+      SUM(ul.estimated_cost)::DECIMAL(10, 6) AS total_cost
+    FROM 
+      usage_logs ul
+    WHERE 
+      ul.user_id = get_user_usage_by_period.user_id
+    GROUP BY 
+      time_period
+    ORDER BY 
+      time_period DESC;
+  ELSIF period = 'year' THEN
+    RETURN QUERY
+    SELECT 
+      TO_CHAR(ul.created_at, 'YYYY') AS time_period,
+      SUM(ul.total_tokens)::BIGINT AS total_tokens,
+      SUM(ul.estimated_cost)::DECIMAL(10, 6) AS total_cost
+    FROM 
+      usage_logs ul
+    WHERE 
+      ul.user_id = get_user_usage_by_period.user_id
+    GROUP BY 
+      time_period
+    ORDER BY 
+      time_period DESC;
+  ELSE
+    -- Fallback auf tägliche Ansicht
+    RETURN QUERY
+    SELECT 
+      TO_CHAR(ul.created_at, 'YYYY-MM-DD') AS time_period,
+      SUM(ul.total_tokens)::BIGINT AS total_tokens,
+      SUM(ul.estimated_cost)::DECIMAL(10, 6) AS total_cost
+    FROM 
+      usage_logs ul
+    WHERE 
+      ul.user_id = get_user_usage_by_period.user_id
+    GROUP BY 
+      time_period
+    ORDER BY 
+      time_period DESC;
+  END IF;
+END;
+$$;
+
+-- 3. Funktion zum Abrufen der Token-Nutzung einer bestimmten Konversation
+CREATE OR REPLACE FUNCTION get_conversation_usage(conversation_id UUID)
+RETURNS TABLE (
+  message_id UUID,
+  created_at TIMESTAMP WITH TIME ZONE,
+  prompt_tokens BIGINT,
+  completion_tokens BIGINT,
+  total_tokens BIGINT,
+  estimated_cost DECIMAL(10, 6)
+)
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+BEGIN
+  RETURN QUERY
+  SELECT 
+    ul.message_id,
+    ul.created_at,
+    ul.prompt_tokens::BIGINT,
+    ul.completion_tokens::BIGINT,
+    ul.total_tokens::BIGINT,
+    ul.estimated_cost::DECIMAL(10, 6)
+  FROM 
+    usage_logs ul
+  WHERE 
+    ul.conversation_id = get_conversation_usage.conversation_id
+  ORDER BY 
+    ul.created_at;
+END;
+$$;
+
+-- Erteile Berechtigungen für die Funktionen
+GRANT EXECUTE ON FUNCTION get_user_model_usage TO authenticated;
+GRANT EXECUTE ON FUNCTION get_user_usage_by_period TO authenticated;
+GRANT EXECUTE ON FUNCTION get_conversation_usage TO authenticated;