feat: Replace SSE with WebSocket for UI notifications (#36965)

* Closes #36942
* Fixes #19265 

Replaces the SSE-based push channel (`/user/events`) with a WebSocket
endpoint (`/-/ws`).

### What changes

- **New `/-/ws` endpoint** (authenticated). One WebSocket per origin,
shared across tabs via a single `SharedWorker`.
- **Pubsub broker** (`services/pubsub`) for fan-out by topic, behind a
`Broker` interface. `MemoryBroker` is the default (single process); a
Redis backend is available for multi-process setups, configured via
`[websocket].PUBSUB_TYPE` / `PUBSUB_CONN_STR`. The internal Gitea queue
was not usable here because it has FIFO/single-consumer semantics.
- **Push-only event production.** Events are emitted by write-triggered
notifiers — `NotificationCountChange`, `PublishStopwatchesForUser`, and
the logout publisher — wired into the existing `notify.Notifier`
interface. No server-side pollers.
- **Typed pub/sub on the client.** `web_src/js/modules/worker.ts` is a
singleton transport; features subscribe per event type via
`onUserEvent('notification-count', cb)` instead of branching on
`event.data.type`.
- **Wire contract** (`UserEventType` union) is shared between the worker
and consumers via `web_src/js/types.ts`, kept in sync with
`services/websocket/events.go`.
- **Client-side periodic polling fallback** kicks in only when the
WebSocket cannot be established (e.g. proxy blocks WS, browser lacks
module-SharedWorker support).

### What's removed

- `modules/eventsource` (SSE manager, run loop, messenger).
- `/user/events` route and `tests/integration/eventsource_test.go`.
- All server-side polling for stopwatches and notification counts.

### Stopwatch multi-tab fix

The navbar stopwatch icon was previously rendered conditionally on `{{if
$activeStopwatch}}`, so tabs loaded before the timer started had no DOM
element to update. The icon and popup are now always rendered (toggled
with `tw-hidden`), and the start/stop/cancel handlers POST silently so
all open tabs reflect the change in real time.

### Deployment note

WebSocket needs the upgrade headers to pass through a reverse proxy,
e.g. for nginx:

```nginx
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
```

Without them the WebSocket cannot be established, and after 3
consecutive failed opens the shared worker signals `push-unavailable`:
the notification count and stopwatch fall back to periodic polling on
the existing `[ui.notification]` timeouts. Real-time push is lost, the
features keep working. The reverse-proxy docs need the same note (see
the `docs-update-needed` label).

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Epid <rexmrj@gmail.com>

tests/integration/editor_test.go

@@ -420,7 +420,7 @@ func testForkToEditFile(t *testing.T, session *TestSession, user, owner, repo, b
 		resp := session.MakeRequest(t, req, http.StatusOK)
 		htmlDoc := NewHTMLParser(t, resp.Body)
 
-		uploadForm := htmlDoc.doc.Find(".form-fetch-action")
+		uploadForm := htmlDoc.doc.Find(".repo-file-upload.form-fetch-action")
 		formAction := uploadForm.AttrOr("action", "")
 		assert.Equal(t, fmt.Sprintf("/%s/%s-1/_upload/%s/%s?from_base_branch=%s&foo=bar", user, repo, branch, filePath, branch), formAction)
 		uploadLink := uploadForm.Find(".dropzone").AttrOr("data-link-url", "")

tests/integration/eventsource_test.go

@@ -1,84 +0,0 @@
-// Copyright 2020 The Gitea Authors. All rights reserved.
-// SPDX-License-Identifier: MIT
-
-package integration
-
-import (
-	"fmt"
-	"net/http"
-	"testing"
-	"time"
-
-	activities_model "gitea.dev/models/activities"
-	auth_model "gitea.dev/models/auth"
-	repo_model "gitea.dev/models/repo"
-	"gitea.dev/models/unittest"
-	user_model "gitea.dev/models/user"
-	"gitea.dev/modules/eventsource"
-	api "gitea.dev/modules/structs"
-	"gitea.dev/tests"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func TestEventSourceManagerRun(t *testing.T) {
-	defer tests.PrepareTestEnv(t)()
-	manager := eventsource.GetManager()
-
-	eventChan := manager.Register(2)
-	defer func() {
-		manager.Unregister(2, eventChan)
-		// ensure the eventChan is closed
-		for {
-			_, ok := <-eventChan
-			if !ok {
-				break
-			}
-		}
-	}()
-	expectNotificationCountEvent := func(count int64) func() bool {
-		return func() bool {
-			select {
-			case event, ok := <-eventChan:
-				if !ok {
-					return false
-				}
-				data, ok := event.Data.(activities_model.UserIDCount)
-				if !ok {
-					return false
-				}
-				return event.Name == "notification-count" && data.Count == count
-			default:
-				return false
-			}
-		}
-	}
-
-	user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
-	repo1 := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
-	thread5 := unittest.AssertExistsAndLoadBean(t, &activities_model.Notification{ID: 5})
-	assert.NoError(t, thread5.LoadAttributes(t.Context()))
-	session := loginUser(t, user2.Name)
-	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteNotification, auth_model.AccessTokenScopeWriteRepository)
-
-	// -- mark notifications as read --
-	req := NewRequest(t, "GET", "/api/v1/notifications?status-types=unread").
-		AddTokenAuth(token)
-	resp := session.MakeRequest(t, req, http.StatusOK)
-
-	apiNL := DecodeJSON(t, resp, []api.NotificationThread{})
-	assert.Len(t, apiNL, 2)
-
-	lastReadAt := "2000-01-01T00%3A50%3A01%2B00%3A00" // 946687801 <- only Notification 4 is in this filter ...
-	req = NewRequest(t, "PUT", fmt.Sprintf("/api/v1/repos/%s/%s/notifications?last_read_at=%s", user2.Name, repo1.Name, lastReadAt)).
-		AddTokenAuth(token)
-	session.MakeRequest(t, req, http.StatusResetContent)
-
-	req = NewRequest(t, "GET", "/api/v1/notifications?status-types=unread").
-		AddTokenAuth(token)
-	resp = session.MakeRequest(t, req, http.StatusOK)
-	apiNL = DecodeJSON(t, resp, []api.NotificationThread{})
-	assert.Len(t, apiNL, 1)
-
-	assert.Eventually(t, expectNotificationCountEvent(1), 30*time.Second, 1*time.Second)
-}

tests/integration/signin_test.go

@@ -177,8 +177,8 @@ func TestRequireSignInView(t *testing.T) {
 		require.False(t, setting.Service.BlockAnonymousAccessExpensive)
 		req := NewRequest(t, "GET", "/user2/repo1/src/branch/master")
 		MakeRequest(t, req, http.StatusOK)
-		req = NewRequest(t, "GET", "/user/events")
-		MakeRequest(t, req, http.StatusOK)
+		req = NewRequest(t, "GET", "/-/ws")
+		MakeRequest(t, req, http.StatusUpgradeRequired)
 	})
 	t.Run("RequireSignInView", func(t *testing.T) {
 		defer test.MockVariableValue(&setting.Service.RequireSignInViewStrict, true)()
@@ -194,7 +194,7 @@ func TestRequireSignInView(t *testing.T) {
 
 		req := NewRequest(t, "GET", "/user2/repo1")
 		MakeRequest(t, req, http.StatusOK)
-		req = NewRequest(t, "GET", "/user/events")
+		req = NewRequest(t, "GET", "/-/ws")
 		MakeRequest(t, req, http.StatusSeeOther)
 
 		req = NewRequest(t, "GET", "/user2/repo1/src/branch/master")