feat: a calendar to subscribe to, and the backlog's corners

- Each person can subscribe their dates in Google Calendar, Outlook or
  Apple Calendar: GET /api/calendar/{token}.ics (no session) brings
  their unfinished tickets with a due date (assigned or followed), the
  planned and running sprints and the planned releases of their
  projects, as all-day events linking to the web. The token is made,
  renewed or dropped under /me/calendar (and in GraphQL); in the web,
  from «Calendario» in «Mi trabajo».
- The backlog panel keeps the selected rows' background inside its
  rounded corners.

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

apps/api/openapi.json

@@ -380,6 +380,114 @@
         "security": []
       }
     },
+    "/api/calendar/{file}": {
+      "get": {
+        "description": "Unfinished tickets with a due date (assigned or followed), planned and running sprints, and planned releases with a date, as all-day events.",
+        "operationId": "CalendarController_ics",
+        "parameters": [
+          {
+            "name": "file",
+            "required": true,
+            "in": "path",
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": ""
+          }
+        },
+        "summary": "A calendar to subscribe to (`{token}.ics`, no session)",
+        "tags": [
+          "Users"
+        ],
+        "security": []
+      }
+    },
+    "/api/me/calendar": {
+      "get": {
+        "operationId": "CalendarController_mine",
+        "parameters": [],
+        "responses": {
+          "200": {
+            "description": "",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/CalendarFeedDto"
+                }
+              }
+            }
+          },
+          "204": {
+            "description": "I have none"
+          }
+        },
+        "security": [
+          {
+            "pireon-oauth": []
+          },
+          {
+            "pireon": []
+          }
+        ],
+        "summary": "My calendar URL, if I made one",
+        "tags": [
+          "Users"
+        ]
+      },
+      "post": {
+        "operationId": "CalendarController_create",
+        "parameters": [],
+        "responses": {
+          "200": {
+            "description": "",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/CalendarFeedDto"
+                }
+              }
+            }
+          }
+        },
+        "security": [
+          {
+            "pireon-oauth": []
+          },
+          {
+            "pireon": []
+          }
+        ],
+        "summary": "A new secret calendar URL (the previous one stops working)",
+        "tags": [
+          "Users"
+        ]
+      },
+      "delete": {
+        "operationId": "CalendarController_revoke",
+        "parameters": [],
+        "responses": {
+          "204": {
+            "description": ""
+          }
+        },
+        "security": [
+          {
+            "pireon-oauth": []
+          },
+          {
+            "pireon": []
+          }
+        ],
+        "summary": "My calendar URL stops working",
+        "tags": [
+          "Users"
+        ]
+      }
+    },
     "/api/projects": {
       "get": {
         "operationId": "ProjectsController_mine",
@@ -9967,6 +10075,22 @@
           "isActive"
         ]
       },
+      "CalendarFeedDto": {
+        "type": "object",
+        "properties": {
+          "token": {
+            "type": "string",
+            "description": "Secret of the calendar URL: GET /api/calendar/{token}.ics (iCalendar, no session)"
+          },
+          "createdAt": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "token",
+          "createdAt"
+        ]
+      },
       "UserRefDto": {
         "type": "object",
         "properties": {