feat: sprints with burndown and carry-over

Plan sprints with dates and a goal, run one at a time per project, and
put tickets in them from the ticket page. The Sprints tab follows the one
under way with its progress and a burndown in tickets or points against
the ideal line. Closing a sprint sends what was left to the next one or
back to the backlog; the board can be filtered by sprint.

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

apps/api/schema.gql

@@ -176,6 +176,17 @@ input CreateReleaseInput {
   targetDate: String
 }
 
+input CreateSprintInput {
+  """YYYY-MM-DD, included"""
+  endDate: String!
+  goal: String
+  name: String!
+  projectId: ID!
+
+  """YYYY-MM-DD"""
+  startDate: String!
+}
+
 type CreatedResolved {
   created: Int!
   resolved: Int!
@@ -249,6 +260,7 @@ type Issue {
   rank: String!
   release: ReleaseRef
   reporter: UserRef!
+  sprint: SprintRef
 
   """A status id of the project's settings"""
   status: String!
@@ -278,6 +290,9 @@ input IssueFilterInput {
   categories: [StatusCategory!]
   labels: [String!]
 
+  """Only tickets in no sprint"""
+  noSprint: Boolean
+
   """Only the tickets hanging from this one"""
   parentId: ID
   priorities: [IssuePriority!]
@@ -287,6 +302,7 @@ input IssueFilterInput {
   """Matches key, title or description"""
   search: String
   sort: IssueSort = RECENT
+  sprintId: ID
   statuses: [String!]
   types: [String!]
   unassigned: Boolean
@@ -388,10 +404,18 @@ type Mutation {
   """Move a ticket through the workflow (incl. QA)"""
   changeIssueStatus(input: ChangeIssueStatusInput!): CommandResult!
   changeProjectMemberRole(input: ProjectMemberInput!): CommandResult!
+
+  """
+  Close the sprint under way. Unfinished tickets move to carryOverToSprintId, or back to the backlog when it is null.
+  """
+  closeSprint(carryOverToSprintId: ID, sprintId: ID!): CommandResult!
   createIssue(input: CreateIssueInput!): CommandResult!
   createProject(input: CreateProjectInput!): CommandResult!
   createRelease(input: CreateReleaseInput!): CommandResult!
 
+  """Plan a sprint (owners and admins)"""
+  createSprint(input: CreateSprintInput!): CommandResult!
+
   """Author or project admin"""
   deleteComment(commentId: ID!): CommandResult!
 
@@ -402,6 +426,9 @@ type Mutation {
 
   """Delete a view: whoever saved it, or an admin if it is shared"""
   deleteSavedFilter(id: ID!): Boolean!
+
+  """Delete a sprint that never started; its tickets go back to the backlog"""
+  deleteSprint(sprintId: ID!): CommandResult!
   editComment(body: String!, commentId: ID!): CommandResult!
 
   """Relate tickets, e.g. FE DEPENDS_ON BE, QA TESTS FE"""
@@ -435,6 +462,12 @@ type Mutation {
 
   """Put a ticket in a release (null removes it)"""
   setIssueRelease(issueId: ID!, releaseId: ID): CommandResult!
+
+  """Put a ticket in a sprint (null: back to the backlog)"""
+  setIssueSprint(issueId: ID!, sprintId: ID): CommandResult!
+
+  """Start a planned sprint (only one under way per project)"""
+  startSprint(sprintId: ID!): CommandResult!
   unlinkIssues(input: LinkIssuesInput!): CommandResult!
 
   """Stop following a ticket"""
@@ -451,6 +484,7 @@ type Mutation {
   """
   updateProjectSettings(projectId: ID!, settings: ProjectSettingsInput!): CommandResult!
   updateRelease(input: UpdateReleaseInput!): CommandResult!
+  updateSprint(input: UpdateSprintInput!): CommandResult!
 
   """
   Follow a ticket: be told when it moves, is reassigned or gets a comment
@@ -517,6 +551,7 @@ type Project {
 
     """Matches key, title or description"""
     search: String
+    sprintId: ID
     types: [String!]
     unassigned: Boolean
   ): [BoardColumn!]!
@@ -668,6 +703,12 @@ type Query {
 
   """My views of the project's board, then the shared ones"""
   savedFilters(projectId: ID!): [SavedFilter!]!
+  sprint(id: ID!): Sprint!
+
+  """
+  A project's sprints: the one under way, the planned ones, then the closed ones
+  """
+  sprints(projectId: ID!): [Sprint!]!
 
   """Planned releases of all my projects, soonest target date first"""
   upcomingReleases(limit: Int! = 10): [Release!]!
@@ -784,6 +825,73 @@ input SavedFilterCriteriaInput {
   unassigned: Boolean
 }
 
+"""A time-boxed iteration: the tickets the team commits to"""
+type Sprint {
+  burndown: SprintBurndown!
+  closedAt: String
+  createdAt: String!
+
+  """Last day (included), YYYY-MM-DD"""
+  endDate: String!
+  goal: String
+  id: ID!
+
+  """Tickets in this sprint, in backlog order"""
+  issues(limit: Int! = 100, offset: Int! = 0): IssuePage!
+  name: String!
+  progress: SprintProgress!
+  projectId: ID!
+
+  """First day, YYYY-MM-DD"""
+  startDate: String!
+  startedAt: String
+  status: SprintStatus!
+  version: Int!
+}
+
+"""
+Per day of the sprint: tickets in it, still open, and their points (null: days to come). `ideal` falls from the first day to zero.
+"""
+type SprintBurndown {
+  dates: [String!]!
+  ideal: [Float!]!
+  remaining: [Int]!
+  remainingPoints: [Int]!
+  scope: [Int]!
+  sprintId: ID!
+}
+
+type SprintChange {
+  action: String!
+  actorId: ID!
+
+  """Null: deleted"""
+  sprint: Sprint
+  sprintId: ID!
+  version: Int!
+}
+
+type SprintProgress {
+  """Done or cancelled"""
+  finished: Int!
+  finishedStoryPoints: Int!
+  percent: Int!
+  storyPoints: Int!
+  total: Int!
+}
+
+type SprintRef {
+  id: ID!
+  name: String!
+}
+
+"""PLANNED, ACTIVE (one per project at a time) or CLOSED"""
+enum SprintStatus {
+  ACTIVE
+  CLOSED
+  PLANNED
+}
+
 """
 What a status means, whatever each project calls it. DONE and CANCELLED are finished.
 """
@@ -820,6 +928,7 @@ type Subscription {
   notificationAdded: Notification!
   projectChanged(projectId: ID!): ProjectChange!
   releaseChanged(projectId: ID!): ReleaseChange!
+  sprintChanged(projectId: ID!): SprintChange!
 }
 
 type Throughput {
@@ -865,6 +974,14 @@ input UpdateReleaseInput {
   targetDate: String
 }
 
+input UpdateSprintInput {
+  endDate: String
+  goal: String
+  name: String
+  sprintId: ID!
+  startDate: String
+}
+
 """User managed by the Pireon identity server"""
 type User {
   email: String!