feat: rebuild math life around marks and directed endings

backend/math_life/models.py

@@ -127,6 +127,42 @@ class StoryChoice(models.Model):
         ordering = ["sequence"]
 
 
+class StoryMark(models.Model):
+    user = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name="story_marks",
+    )
+    story = models.ForeignKey(
+        Story,
+        on_delete=models.CASCADE,
+        related_name="collected_marks",
+    )
+    source_run = models.ForeignKey(
+        StoryRun,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        related_name="acquired_marks",
+    )
+    code = models.CharField(max_length=60)
+    name = models.CharField(max_length=80)
+    domain = models.CharField(max_length=40)
+    acquired_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        constraints = [
+            models.UniqueConstraint(
+                fields=("user", "story", "code"),
+                name="unique_user_story_mark",
+            )
+        ]
+        ordering = ["acquired_at"]
+
+    def __str__(self):
+        return f"{self.user} · {self.name}"
+
+
 class UserRelationship(models.Model):
     user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
     character = models.ForeignKey(Character, on_delete=models.CASCADE)