chore: Remove admin-ui, improve .env.example, add comprehensive README

- Removed deprecated admin-ui Rust application
- Updated .env.example with better organization and comments
- Added comprehensive README.md with:
  - Architecture overview
  - Quick start guide
  - Development instructions
  - Feature documentation
  - Environment variable reference
  - API documentation link

.env.example

@@ -1,9 +1,48 @@
+# Stripstream Librarian - Environment Configuration
+
+# =============================================================================
+# REQUIRED - Change these values in production!
+# =============================================================================
+
+# Master key for Meilisearch authentication (required)
+MEILI_MASTER_KEY=change-me-in-production
+
+# Bootstrap token for initial API admin access (required)
+# Use this token for the first API calls before creating proper API tokens
+API_BOOTSTRAP_TOKEN=change-me-in-production
+
+# =============================================================================
+# Services Configuration
+# =============================================================================
+
+# API Service
 API_LISTEN_ADDR=0.0.0.0:8080
-BACKOFFICE_PORT=8082
 API_BASE_URL=http://api:8080
+
+# Indexer Service  
 INDEXER_LISTEN_ADDR=0.0.0.0:8081
 INDEXER_SCAN_INTERVAL_SECONDS=5
+
+# Backoffice Web UI
+BACKOFFICE_PORT=8082
+
+# =============================================================================
+# Database Configuration
+# =============================================================================
+
+# PostgreSQL connection string
 DATABASE_URL=postgres://stripstream:stripstream@postgres:5432/stripstream
+
+# =============================================================================
+# Search Configuration
+# =============================================================================
+
+# Meilisearch connection URL
 MEILI_URL=http://meilisearch:7700
-MEILI_MASTER_KEY=change-me
-API_BOOTSTRAP_TOKEN=change-me-bootstrap-token
+
+# =============================================================================
+# Optional - Development only
+# =============================================================================
+
+# Path to libraries directory (default: /libraries in Docker)
+# LIBRARIES_ROOT_PATH=/libraries