feat(accounts): implement user accounts, sessions, and dashboards

Introduce Stage 4 features to support multi-user accounts, cookie-based web sessions, and personal dashboards.

Changes include:
- Adding `/register` to bootstrap the first admin account and `/login`/`/logout` for session management.
- Creating a personal dashboard (`/app`) to display owned boxes, storage usage, and upload history.
- Implementing admin user management (`/admin/users`) for generating invite links and managing user states.
- Updating the bbolt database schema to store users, sessions, invites, and collections.
- Adding `golang.org/x/crypto` for password hashing and introducing unit tests for account handlers.

backend/libs/handlers/accounts_test.go

@@ -0,0 +1,165 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"warpbox.dev/backend/libs/services"
+)
+
+func TestLoggedInUploadStoresOwnerAndAnonymousUploadDoesNot(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	user, err := app.authService.CreateBootstrapUser("daniel", "daniel@example.test", "password123")
+	if err != nil {
+		t.Fatalf("CreateBootstrapUser returned error: %v", err)
+	}
+	_, token, err := app.authService.Login("daniel@example.test", "password123")
+	if err != nil {
+		t.Fatalf("Login returned error: %v", err)
+	}
+
+	request := multipartUploadRequest(t, "/api/v1/upload", "file", "owned.txt", "owned")
+	request.Header.Set("Accept", "application/json")
+	request.AddCookie(&http.Cookie{Name: userSessionCookieName, Value: token})
+	response := httptest.NewRecorder()
+	app.Upload(response, request)
+	if response.Code != http.StatusCreated {
+		t.Fatalf("owned upload status = %d, body = %s", response.Code, response.Body.String())
+	}
+	var ownedPayload services.UploadResult
+	if err := json.Unmarshal(response.Body.Bytes(), &ownedPayload); err != nil {
+		t.Fatalf("json.Unmarshal owned returned error: %v", err)
+	}
+	ownedBox, err := app.uploadService.GetBox(ownedPayload.BoxID)
+	if err != nil {
+		t.Fatalf("GetBox owned returned error: %v", err)
+	}
+	if ownedBox.OwnerID != user.ID {
+		t.Fatalf("owned OwnerID = %q, want %q", ownedBox.OwnerID, user.ID)
+	}
+
+	owned := uploadThroughApp(t, app)
+	anonymous, err := app.uploadService.GetBox(owned.BoxID)
+	if err != nil {
+		t.Fatalf("GetBox anonymous returned error: %v", err)
+	}
+	if anonymous.OwnerID != "" {
+		t.Fatalf("anonymous OwnerID = %q, want empty", anonymous.OwnerID)
+	}
+
+	boxes, err := app.uploadService.ListBoxes(0)
+	if err != nil {
+		t.Fatalf("ListBoxes returned error: %v", err)
+	}
+	foundOwned := false
+	for _, box := range boxes {
+		if box.OwnerID == user.ID {
+			foundOwned = true
+		}
+	}
+	if !foundOwned {
+		t.Fatalf("logged-in upload did not store owner id %q", user.ID)
+	}
+}
+
+func TestInviteHandlerCreatesUserAndMarksInviteUsed(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	admin, err := app.authService.CreateBootstrapUser("admin", "admin@example.test", "password123")
+	if err != nil {
+		t.Fatalf("CreateBootstrapUser returned error: %v", err)
+	}
+	invite, err := app.authService.CreateInvite("friend@example.test", services.UserRoleUser, admin.ID, 0)
+	if err != nil {
+		t.Fatalf("CreateInvite returned error: %v", err)
+	}
+
+	request := httptest.NewRequest(http.MethodPost, "/invite/"+invite.Token, strings.NewReader("username=friend&password=password123"))
+	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	request.SetPathValue("token", invite.Token)
+	response := httptest.NewRecorder()
+	app.InvitePost(response, request)
+	if response.Code != http.StatusSeeOther {
+		t.Fatalf("InvitePost status = %d, body = %s", response.Code, response.Body.String())
+	}
+	if _, err := app.authService.AcceptInvite(invite.Token, "friend", "password123"); err == nil {
+		t.Fatalf("invite token remained reusable")
+	}
+}
+
+func TestNonOwnerCannotManageOwnedBox(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	owner, err := app.authService.CreateBootstrapUser("owner", "owner@example.test", "password123")
+	if err != nil {
+		t.Fatalf("CreateBootstrapUser returned error: %v", err)
+	}
+	invite, err := app.authService.CreateInvite("other@example.test", services.UserRoleUser, owner.ID, 0)
+	if err != nil {
+		t.Fatalf("CreateInvite returned error: %v", err)
+	}
+	other, err := app.authService.AcceptInvite(invite.Token, "other", "password123")
+	if err != nil {
+		t.Fatalf("AcceptInvite returned error: %v", err)
+	}
+
+	result := createOwnedBoxThroughApp(t, app, owner.ID)
+	if err := app.uploadService.RenameOwnedBox(result.BoxID, other.ID, "stolen"); err == nil {
+		t.Fatalf("RenameOwnedBox allowed non-owner")
+	}
+}
+
+func TestAdminUploadBypassesMaxUploadSize(t *testing.T) {
+	app, cleanup := newTestApp(t)
+	defer cleanup()
+
+	_, err := app.authService.CreateBootstrapUser("admin", "admin@example.test", "password123")
+	if err != nil {
+		t.Fatalf("CreateBootstrapUser returned error: %v", err)
+	}
+	_, token, err := app.authService.Login("admin@example.test", "password123")
+	if err != nil {
+		t.Fatalf("Login returned error: %v", err)
+	}
+
+	request := multipartUploadRequest(t, "/api/v1/upload", "file", "large.txt", strings.Repeat("x", int(app.uploadService.MaxUploadSize())+1))
+	request.Header.Set("Accept", "application/json")
+	request.AddCookie(&http.Cookie{Name: userSessionCookieName, Value: token})
+	response := httptest.NewRecorder()
+	app.Upload(response, request)
+	if response.Code != http.StatusCreated {
+		t.Fatalf("admin upload status = %d, body = %s", response.Code, response.Body.String())
+	}
+}
+
+func createOwnedBoxThroughApp(t *testing.T, app *App, userID string) services.UploadResult {
+	t.Helper()
+	user, err := app.authService.UserByID(userID)
+	if err != nil {
+		t.Fatalf("UserByID returned error: %v", err)
+	}
+	_, token, err := app.authService.Login(user.Email, "password123")
+	if err != nil {
+		t.Fatalf("Login returned error: %v", err)
+	}
+	request := multipartUploadRequest(t, "/api/v1/upload", "file", "owned.txt", "owned")
+	request.Header.Set("Accept", "application/json")
+	request.AddCookie(&http.Cookie{Name: userSessionCookieName, Value: token})
+	response := httptest.NewRecorder()
+	app.Upload(response, request)
+	if response.Code != http.StatusCreated {
+		t.Fatalf("upload status = %d, body = %s", response.Code, response.Body.String())
+	}
+	var payload services.UploadResult
+	if err := json.Unmarshal(response.Body.Bytes(), &payload); err != nil {
+		t.Fatalf("json.Unmarshal returned error: %v", err)
+	}
+	return payload
+}