fix: resolve SSH key and errcheck linter issues

Deploy workflow fixes:
- Add tr -d '\r' to strip carriage returns from SSH key
- Set chmod 700 on .ssh directory for proper permissions
- Suppress ssh-keyscan stderr output

Handler code fixes:
- Check json.Encode() return values in errors.go (2 locations)
- Check json.Encode() return value in health.go
- Add log import to health.go
- Log encoding errors instead of silently ignoring

Resolves:
- "Load key: error in libcrypto" SSH deployment error
- 3 errcheck linter warnings

internal/handlers/health.go

@@ -2,6 +2,7 @@ package handlers
 
 import (
 	"encoding/json"
+	"log"
 	"net/http"
 	"time"
 )
@@ -35,5 +36,8 @@ func (h *HealthHandler) Check(w http.ResponseWriter, r *http.Request) {
 
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(http.StatusOK)
-	json.NewEncoder(w).Encode(response)
+	if err := json.NewEncoder(w).Encode(response); err != nil {
+		// Log error but don't change response status (already written)
+		log.Printf("ERROR encoding health check response: %v", err)
+	}
 }