Download REST API endpoints (#72)

* backend and frontend hotfixes, see message

Improved rendering on the frontend by cutting unecessary useStates.
Backend side, downloads now auto resume even on application kill.

* download rest api endpoints, general code refactor

* download request json mappings

server/handlers/login.go

@@ -0,0 +1,65 @@
+package handlers
+
+import (
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/goccy/go-json"
+	"github.com/golang-jwt/jwt/v5"
+	"github.com/marcopeocchi/yt-dlp-web-ui/server/config"
+)
+
+type LoginRequest struct {
+	Secret string `json:"secret"`
+}
+
+func Login(w http.ResponseWriter, r *http.Request) {
+	req := new(LoginRequest)
+	err := json.NewDecoder(r.Body).Decode(&req)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	if config.Instance().GetConfig().RPCSecret != req.Secret {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	expiresAt := time.Now().Add(time.Hour * 24 * 30)
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
+		"expiresAt": expiresAt,
+	})
+
+	tokenString, err := token.SignedString([]byte(os.Getenv("JWT_SECRET")))
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	cookie := &http.Cookie{
+		Name:     TOKEN_COOKIE_NAME,
+		HttpOnly: true,
+		Secure:   false,
+		Expires:  expiresAt, // 30 days
+		Value:    tokenString,
+		Path:     "/",
+	}
+
+	http.SetCookie(w, cookie)
+}
+
+func Logout(w http.ResponseWriter, r *http.Request) {
+	cookie := &http.Cookie{
+		Name:     TOKEN_COOKIE_NAME,
+		HttpOnly: true,
+		Secure:   false,
+		Expires:  time.Now(),
+		Value:    "",
+		Path:     "/",
+	}
+
+	http.SetCookie(w, cookie)
+}