feat: protect write endpoints with JWT auth (story #08)

Add bcrypt user file auth, JWT middleware on all write routes, Pinia
authStore with localStorage persistence, login view with redirect
support, and v-if guards on all CRUD controls and admin nav link.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/handler/auth_handler.go

@@ -0,0 +1,44 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/labstack/echo/v4"
+
+	"osdb/internal/auth"
+)
+
+// AuthHandler handles authentication endpoints.
+type AuthHandler struct {
+	users     map[string]string
+	jwtSecret string
+}
+
+// NewAuthHandler creates an AuthHandler with the given user map and JWT secret.
+func NewAuthHandler(users map[string]string, jwtSecret string) *AuthHandler {
+	return &AuthHandler{users: users, jwtSecret: jwtSecret}
+}
+
+type loginRequest struct {
+	Username string `json:"username"`
+	Password string `json:"password"`
+}
+
+// Login handles POST /api/v1/auth/login.
+func (h *AuthHandler) Login(c echo.Context) error {
+	var req loginRequest
+	if err := c.Bind(&req); err != nil || req.Username == "" {
+		return c.JSON(http.StatusUnauthorized, map[string]string{"error": "invalid credentials"})
+	}
+
+	if !auth.VerifyPassword(h.users, req.Username, req.Password) {
+		return c.JSON(http.StatusUnauthorized, map[string]string{"error": "invalid credentials"})
+	}
+
+	token, err := auth.GenerateJWT(req.Username, h.jwtSecret)
+	if err != nil {
+		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "token generation failed"})
+	}
+
+	return c.JSON(http.StatusOK, map[string]string{"token": token})
+}

backend/internal/handler/auth_handler_test.go

@@ -0,0 +1,75 @@
+package handler_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"golang.org/x/crypto/bcrypt"
+
+	"github.com/labstack/echo/v4"
+
+	"osdb/internal/handler"
+)
+
+func makeUsersMap(username, password string) map[string]string {
+	h, _ := bcrypt.GenerateFromPassword([]byte(username+":"+password), bcrypt.MinCost)
+	return map[string]string{username: string(h)}
+}
+
+func TestAuthHandler_Login_ValidCredentials(t *testing.T) {
+	users := makeUsersMap("admin", "secret")
+	h := handler.NewAuthHandler(users, "jwttest")
+
+	body := `{"username":"admin","password":"secret"}`
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/login", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	c := echo.New().NewContext(req, rec)
+
+	if err := h.Login(c); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if rec.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d — body: %s", rec.Code, rec.Body.String())
+	}
+	if !strings.Contains(rec.Body.String(), "token") {
+		t.Errorf("expected 'token' in response, got: %s", rec.Body.String())
+	}
+}
+
+func TestAuthHandler_Login_InvalidCredentials(t *testing.T) {
+	users := makeUsersMap("admin", "secret")
+	h := handler.NewAuthHandler(users, "jwttest")
+
+	body := `{"username":"admin","password":"wrong"}`
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/login", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	c := echo.New().NewContext(req, rec)
+
+	if err := h.Login(c); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if rec.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401, got %d", rec.Code)
+	}
+}
+
+func TestAuthHandler_Login_MissingBody(t *testing.T) {
+	users := makeUsersMap("admin", "secret")
+	h := handler.NewAuthHandler(users, "jwttest")
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/login", nil)
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	c := echo.New().NewContext(req, rec)
+
+	if err := h.Login(c); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if rec.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401, got %d", rec.Code)
+	}
+}