refactor: implement unified binary architecture

🏗️ **Major Architecture Refactoring: Separate CLI + Server → Unified Binary**

**Key Changes:**
✅ **Unified Binary**: Single 'insertr' binary with subcommands (enhance, serve)
✅ **Preserved Database Architecture**: Maintained sophisticated sqlc multi-DB setup
✅ **Smart Configuration**: Viper + YAML config with CLI flag precedence
✅ **Updated Build System**: Unified justfile, Air, and npm scripts

**Command Structure:**
- `insertr enhance [input-dir]` - Build-time content injection
- `insertr serve` - HTTP API server (dev + production modes)
- `insertr --config insertr.yaml` - YAML configuration support

**Architecture Benefits:**
- **Shared Database Layer**: Single source of truth for content models
- **Flexible Workflows**: Local DB for dev, remote API for production
- **Simple Deployment**: One binary for all use cases
- **Better UX**: Consistent configuration across build and runtime

**Preserved Features:**
- Multi-database support (SQLite + PostgreSQL)
- sqlc code generation and type safety
- Version control system with rollback
- Professional API endpoints
- Content enhancement pipeline

**Development Workflow:**
- `just dev` - Full-stack development (API server + demo site)
- `just serve` - API server only
- `just enhance` - Build-time content injection
- `air` - Hot reload unified binary

**Migration:** Consolidated insertr-cli/ and insertr-server/ → unified root structure

scripts/build.js

@@ -1,15 +1,15 @@
 #!/usr/bin/env node
 
 /**
- * Build script for Insertr library and CLI integration
- * This ensures the CLI always has the latest library version embedded
+ * Build script for Insertr unified binary
+ * This ensures the unified binary always has the latest library version embedded
  */
 
 import { execSync } from 'child_process';
 import fs from 'fs';
 import path from 'path';
 
-console.log('🔨 Building Insertr library and CLI...\n');
+console.log('🔨 Building Insertr unified binary...\n');
 
 // 1. Build the library
 console.log('📦 Building JavaScript library...');
@@ -21,10 +21,10 @@ try {
     process.exit(1);
 }
 
-// 2. Copy built library to CLI assets
-console.log('📁 Copying library to CLI assets...');
+// 2. Copy built library to unified binary assets
+console.log('📁 Copying library to unified binary assets...');
 const srcDir = './lib/dist';
-const destDir = './insertr-cli/pkg/content/assets';
+const destDir = './internal/content/assets';
 
 // Ensure destination directory exists
 fs.mkdirSync(destDir, { recursive: true });
@@ -40,32 +40,21 @@ files.forEach(file => {
 
 console.log('📁 Assets copied successfully\n');
 
-// 3. Build the CLI
-console.log('🔧 Building Go CLI...');
+// 3. Build the unified binary
+console.log('🔧 Building unified Insertr binary...');
 try {
-    execSync('go build -o insertr', { cwd: './insertr-cli', stdio: 'inherit' });
-    console.log('✅ CLI built successfully\n');
+    execSync('go build -o insertr .', { stdio: 'inherit' });
+    console.log('✅ Unified binary built successfully\n');
 } catch (error) {
-    console.error('❌ CLI build failed:', error.message);
-    process.exit(1);
-}
-
-// 4. Build the API Server
-console.log('🔌 Building API Server...');
-try {
-    execSync('go build -o insertr-server ./cmd/server', { cwd: './insertr-server', stdio: 'inherit' });
-    console.log('✅ API Server built successfully\n');
-} catch (error) {
-    console.error('❌ API Server build failed:', error.message);
+    console.error('❌ Unified binary build failed:', error.message);
     process.exit(1);
 }
 
 console.log('🎉 Build complete!\n');
 console.log('📋 What was built:');
 console.log('  • JavaScript library (lib/dist/)');
-console.log('  • Go CLI with embedded library (insertr-cli/insertr)');
-console.log('  • Content API server (insertr-server/insertr-server)');
+console.log('  • Unified Insertr binary with embedded library (./insertr)');
 console.log('\n🚀 Ready to use:');
 console.log('  just dev         # Full-stack development');
-console.log('  just server      # API server only');
-console.log('  cd insertr-cli && ./insertr --help  # CLI tools');
+console.log('  just serve       # API server only');
+console.log('  ./insertr --help # See all commands');