feat: notifications in the app and, optionally, by e-mail

Derived from events and kept per person: whoever a ticket is assigned to,
whoever reports or works on it when it moves, fails QA or gets a comment,
and whoever joins a project. Never about what you did yourself, once per
event. They arrive live through a subscription to a bell in the header,
and are copied by e-mail to whoever turns it on when SMTP_URL is set.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/schema.gql

@@ -342,6 +342,9 @@ type Mutation {
   """Relate tickets, e.g. FE DEPENDS_ON BE, QA TESTS FE"""
   linkIssues(input: LinkIssuesInput!): CommandResult!
 
+  """Mark these as read, or all of them when `ids` is omitted"""
+  markNotificationsRead(ids: [ID!]): Boolean!
+
   """
   Ship the release. Fails while it has unfinished tickets unless force = true.
   """
@@ -357,6 +360,7 @@ type Mutation {
   setIssueRelease(issueId: ID!, releaseId: ID): CommandResult!
   unlinkIssues(input: LinkIssuesInput!): CommandResult!
   updateIssue(input: UpdateIssueInput!): CommandResult!
+  updateNotificationSettings(email: Boolean!): NotificationSettings!
   updateProject(input: UpdateProjectInput!): CommandResult!
 
   """
@@ -366,6 +370,48 @@ type Mutation {
   updateRelease(input: UpdateReleaseInput!): CommandResult!
 }
 
+type MyNotifications {
+  items: [Notification!]!
+
+  """All my unread ones, not just these"""
+  unread: Int!
+}
+
+type Notification {
+  actor: UserRef!
+  createdAt: String!
+  id: ID!
+  issueId: ID
+  issueKey: String
+  kind: NotificationKind!
+  projectId: ID!
+  projectKey: String!
+
+  """Null: unread"""
+  readAt: String
+  summary: String!
+}
+
+"""Why someone is told"""
+enum NotificationKind {
+  ADDED_TO_PROJECT
+  ASSIGNED
+  COMMENTED
+  MENTIONED
+  QA_FAILED
+  REMINDER
+  STATUS_CHANGED
+  WATCHED
+}
+
+type NotificationSettings {
+  """Copies by e-mail"""
+  email: Boolean!
+
+  """Whether this installation can send e-mail at all"""
+  emailAvailable: Boolean!
+}
+
 type Project {
   """
   Statistics of the last `days` days (7-365): created vs resolved, cumulative flow, cycle/lead time, throughput and QA
@@ -498,8 +544,12 @@ type Query {
   """
   myIssues(assignedToMe: Boolean! = true, categories: [StatusCategory!], limit: Int! = 50, offset: Int! = 0, statuses: [String!]): IssuePage!
 
+  """My notifications, newest first, and how many are unread"""
+  myNotifications(limit: Int! = 30, unreadOnly: Boolean! = false): MyNotifications!
+
   """Projects where I am a member"""
   myProjects: [Project!]!
+  notificationSettings: NotificationSettings!
 
   """A project of mine, or any public one (no sign-in needed)"""
   project(
@@ -603,6 +653,9 @@ type Subscription {
 
   """Projects I am added to / removed from"""
   myProjectsChanged: ProjectChange!
+
+  """My notifications, as they happen"""
+  notificationAdded: Notification!
   projectChanged(projectId: ID!): ProjectChange!
   releaseChanged(projectId: ID!): ReleaseChange!
 }