cleanup: remove legacy insertr-cli and insertr-server directories

🧹 **Legacy Code Cleanup**

**Removed Directories:**
- `insertr-cli/` - 23 files removed (replaced by unified binary)
- `insertr-server/` - 24 files removed (replaced by unified binary)

**Updated References:**
- `TODO.md` - Updated file paths to reflect unified structure
- `scripts/dev.js` - Updated required/optional file checks

**Benefits:**
✅ **Single Source of Truth** - No more duplicate code or confusion
✅ **Smaller Repository** - Removed ~47 legacy files and binaries
✅ **Cleaner Development** - Only unified binary approach remains
✅ **Better Maintenance** - No legacy code paths to maintain

**All Functionality Preserved:**
- Database layer: `internal/db/`
- Content logic: `internal/content/`
- API handlers: `internal/api/`
- Commands: `cmd/enhance.go`, `cmd/serve.go`

The unified `insertr` binary now provides all functionality with enhanced architecture and no backwards compatibility baggage.

TODO.md

@@ -7,7 +7,7 @@
 ## ✅ What's Already Built & Working
 
 ### **Complete Foundation**
-- ✅ **Go CLI Client** - Full REST API client with all CRUD operations (`insertr-cli/pkg/content/client.go`)
+- ✅ **Go Content Client** - Full REST API client with all CRUD operations (`internal/content/client.go`)
 - ✅ **JavaScript API Client** - Browser client with same API endpoints (`lib/src/core/api-client.js`)
 - ✅ **Content Types** - Well-defined data structures (`ContentItem`, `ContentResponse`)
 - ✅ **Mock Backend** - Working development server with realistic test data
@@ -111,23 +111,16 @@ Static Site Build ← CLI Enhancement ← Database Content
 
 ## 🗂️ **Next Steps: Server Implementation**
 
-### **Files to Create**
+### **✅ Implemented - Unified Binary Architecture**
 ```
-insertr-server/                          # New HTTP server application
-├── cmd/
-│   └── server/
-│       └── main.go                      # Server entry point
-├── internal/
-│   ├── api/
-│   │   ├── handlers.go                  # HTTP handlers for content endpoints  
-│   │   └── middleware.go                # Auth, CORS, logging middleware
-│   ├── db/
-│   │   ├── sqlite.go                    # SQLite implementation
-│   │   └── migrations/                  # Database schema versions
-│   └── models/
-│       └── content.go                   # Content model (matches existing ContentItem)
-├── go.mod
-└── go.sum
+✅ COMPLETED: All server functionality integrated into unified binary
+cmd/
+├── serve.go                             # Runtime API server command
+└── enhance.go                          # Build-time enhancement command
+internal/
+├── api/                                # HTTP handlers and middleware
+├── db/                                 # Multi-database layer with sqlc
+└── content/                            # Content management logic
 ```
 
 ### **Files to Modify**