feat(sprints): modèle de sprints — domaine, use-cases, persistance et surfaces (backend)

Ticket #10 — introduction du modèle de sprints côté backend.

- Domaine : nouvel agrégat Sprint (sprint.rs), IDs, événements et invariants ;
  rattachement des issues à un sprint (issue.rs) et ports associés.
- Application : use-cases sprints (application/src/sprints) + erreurs dédiées.
- Infrastructure : store de sprints (infrastructure/src/sprints.rs), adaptation
  du store d'issues et exposition MCP via orchestrator/mcp/tickets.rs.
- app-tauri : commandes, state et events pour piloter les sprints depuis l'UI.

Tests domaine/application/infra/app-tauri verts (sprint_usecases, sprint_store,
issue_store, mcp_server).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/app-tauri/src/events.rs

@@ -299,6 +299,52 @@ pub enum DomainEventDto {
         /// New optimistic version.
         version: u64,
     },
+    /// A sprint was created.
+    #[serde(rename_all = "camelCase")]
+    SprintCreated {
+        /// Stable sprint id.
+        sprint_id: String,
+        /// Reorderable order.
+        order: u32,
+    },
+    /// A sprint was renamed.
+    #[serde(rename_all = "camelCase")]
+    SprintRenamed {
+        /// Stable sprint id.
+        sprint_id: String,
+        /// New name.
+        name: String,
+        /// New optimistic version.
+        version: u64,
+    },
+    /// A sprint was reordered.
+    #[serde(rename_all = "camelCase")]
+    SprintReordered {
+        /// Stable sprint id.
+        sprint_id: String,
+        /// New order.
+        order: u32,
+        /// New optimistic version.
+        version: u64,
+    },
+    /// A sprint was deleted.
+    #[serde(rename_all = "camelCase")]
+    SprintDeleted {
+        /// Stable sprint id.
+        sprint_id: String,
+    },
+    /// A ticket changed sprint membership.
+    #[serde(rename_all = "camelCase")]
+    IssueSprintChanged {
+        /// Public ticket reference (`#N`).
+        issue_ref: String,
+        /// Previous sprint id.
+        from: Option<String>,
+        /// New sprint id.
+        to: Option<String>,
+        /// New optimistic version.
+        version: u64,
+    },
     /// An orchestrator request was processed on behalf of a requester agent.
     #[serde(rename_all = "camelCase")]
     OrchestratorRequestProcessed {
@@ -773,6 +819,42 @@ impl From<&DomainEvent> for DomainEventDto {
                 agent_id: agent_id.to_string(),
                 version: version.get(),
             },
+            DomainEvent::SprintCreated { sprint_id, order } => Self::SprintCreated {
+                sprint_id: sprint_id.to_string(),
+                order: order.get(),
+            },
+            DomainEvent::SprintRenamed {
+                sprint_id,
+                name,
+                version,
+            } => Self::SprintRenamed {
+                sprint_id: sprint_id.to_string(),
+                name: name.clone(),
+                version: version.get(),
+            },
+            DomainEvent::SprintReordered {
+                sprint_id,
+                order,
+                version,
+            } => Self::SprintReordered {
+                sprint_id: sprint_id.to_string(),
+                order: order.get(),
+                version: version.get(),
+            },
+            DomainEvent::SprintDeleted { sprint_id } => Self::SprintDeleted {
+                sprint_id: sprint_id.to_string(),
+            },
+            DomainEvent::IssueSprintChanged {
+                issue_ref,
+                from,
+                to,
+                version,
+            } => Self::IssueSprintChanged {
+                issue_ref: issue_ref.to_string(),
+                from: from.map(|id| id.to_string()),
+                to: to.map(|id| id.to_string()),
+                version: version.get(),
+            },
             DomainEvent::OrchestratorRequestProcessed {
                 requester_id,
                 action,
@@ -981,4 +1063,22 @@ mod tests {
         assert_eq!(json["agentId"], agent(11).to_string());
         assert_eq!(json["resetsAtMs"], 1_700_000_000_000_i64);
     }
+
+    #[test]
+    fn issue_sprint_changed_relays_to_dto_and_wire() {
+        let from = domain::SprintId::from_uuid(uuid::Uuid::from_u128(41));
+        let to = domain::SprintId::from_uuid(uuid::Uuid::from_u128(42));
+        let dto = DomainEventDto::from(&DomainEvent::IssueSprintChanged {
+            issue_ref: domain::IssueRef::from(domain::IssueNumber::new(7).unwrap()),
+            from: Some(from),
+            to: Some(to),
+            version: domain::IssueVersion::new(3).unwrap(),
+        });
+        let json = serde_json::to_value(&dto).expect("serialisable");
+        assert_eq!(json["type"], "issueSprintChanged");
+        assert_eq!(json["issueRef"], "#7");
+        assert_eq!(json["from"], from.to_string());
+        assert_eq!(json["to"], to.to_string());
+        assert_eq!(json["version"], 3);
+    }
 }