feat: add download commands (yt, ig, tt, fb) and middleware support

- Add core Middleware support via `core.Default.Use()`
- Implement download command handlers for YouTube, Instagram, TikTok, and Facebook
- Add regex-based URL validation for all download commands
- Add API client for fetching download links
- Add helpers for uploading and sending media to WhatsApp

Co-Authored-By: Claude Opus 4.7 <[email protected]>

go.mod

@@ -3,9 +3,12 @@ module neo
 go 1.25.5
 
 require (
+	github.com/gabriel-vasile/mimetype v1.4.13
+	github.com/joho/godotenv v1.5.1
 	github.com/mattn/go-sqlite3 v1.14.47
 	github.com/mdp/qrterminal/v3 v3.2.1
 	go.mau.fi/whatsmeow v0.0.0-20260630180629-b572e5bcb92b
+	google.golang.org/protobuf v1.36.11
 )
 
 require (
@@ -13,9 +16,7 @@ require (
 	github.com/beeper/argo-go v1.1.2 // indirect
 	github.com/coder/websocket v1.8.15 // indirect
 	github.com/elliotchance/orderedmap/v3 v3.1.0 // indirect
-	github.com/gabriel-vasile/mimetype v1.4.13 // indirect
 	github.com/google/uuid v1.6.0 // indirect
-	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/petermattis/goid v0.0.0-20260330135022-df67b199bc81 // indirect
@@ -30,6 +31,5 @@ require (
 	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/term v0.44.0 // indirect
 	golang.org/x/text v0.38.0 // indirect
-	google.golang.org/protobuf v1.36.11 // indirect
 	rsc.io/qr v0.2.0 // indirect
 )