feat(17-03): implement Telegram bot command handlers

- Add telego v1.8.0 dependency for Telegram Bot API
- Create pkg/bot package with Bot struct holding engine, verifier, recon, storage, registry deps
- Implement 8 command handlers: /help, /scan, /verify, /recon, /status, /stats, /providers, /key
- /key enforced private-chat-only for security (never exposes unmasked keys in groups)
- All other commands use masked keys only
- Handler registration via telego's BotHandler with CommandEqual predicates

pkg/bot/source.go

@@ -0,0 +1,21 @@
+package bot
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/salvacybersec/keyhunter/pkg/engine/sources"
+)
+
+// selectBotSource returns the appropriate Source for a bot scan request.
+// Only file and directory paths are supported (no git, stdin, clipboard, URL).
+func selectBotSource(path string) (sources.Source, error) {
+	info, err := os.Stat(path)
+	if err != nil {
+		return nil, fmt.Errorf("stat %q: %w", path, err)
+	}
+	if info.IsDir() {
+		return sources.NewDirSource(path), nil
+	}
+	return sources.NewFileSource(path), nil
+}