Add initial project documentation

docs/services/shared.md

@@ -0,0 +1,18 @@
+# Shared Package
+
+**Package:** '@nexusai/shared'
+**Location:** 'packages/shared'
+
+## Purpose
+Common utilities and configuration used across all NexusAI services
+Keeping these here avoids duplicating and ensure consistent behavior
+
+# Exports
+
+### 'getEnv(key, defaultValue?)'
+Loads an environment variable by key.  If no default is provided and the variable is missing, throws at startup rather than failing later on.
+```javascript
+const { getEnv } = require('@nexusai/shared');
+const PORT = getEnv('PORT', '3002');         // optional — falls back to 3002
+const DB   = getEnv('SQLITE_PATH');          // required — throws if missing
+```