feat(formbuilder): fix tenancy bugs, add admin + services

Fix multi-tenancy/integrity bugs in the models: Form.slug and Field.key
were globally unique (unique=True), so two clubs couldn't reuse a form
slug and two forms couldn't reuse a field key — make slug unique per club
(constraint already present) and key unique per form. Add a
(submission, field) uniqueness constraint on Answer.

Register all four models in the admin (Field inline on Form, Answer inline
on Submission) and add formbuilder to the admin registration smoke test.

Add a service layer:
- submit_form(form, member, data): enforces is_active / login_required /
  open window / max_submissions, validates required + choice fields, and
  writes a Submission with Answers atomically (FormSubmissionError carries
  per-field errors).
- build_form(form): a live django.forms.Form built from a Form's active
  fields, mapping each FieldType to the matching form field.
- form_report(form): a tabular overview of every submission's answers plus
  per-value tallies for choice-type fields.

Full suite at 100% coverage.

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

formbuilder/models.py

@@ -0,0 +1,95 @@
+from django.db import models
+from django.db.models import UniqueConstraint
+from django.utils.translation import gettext_lazy as _
+
+from clubmanager.base import ClubScopedModel, UUIDModel
+from members.models import Member
+
+
+class Form(ClubScopedModel):
+    title = models.CharField(_("title"), max_length=255)
+    slug = models.SlugField(_("slug"))
+    description = models.TextField(_("description"), blank=True)
+
+    is_active = models.BooleanField(_("is active?"), default=True)
+    login_required = models.BooleanField(_("login required?"), default=False)
+
+    opens_at = models.DateTimeField(_("opens at"), blank=True, null=True)
+    closes_at = models.DateTimeField(_("closes at"), blank=True, null=True)
+    max_submissions_per_user = models.PositiveIntegerField(_("max submissions per user"), blank=True, null=True)
+
+    class Meta:
+        verbose_name = _("form")
+        verbose_name_plural = _("forms")
+        ordering = ["title"]
+        constraints = [
+            UniqueConstraint(fields=["club", "slug"], name="unique_form_slug_per_club"),
+        ]
+
+    def __str__(self):
+        return self.title
+
+
+class Field(UUIDModel):
+    class FieldType(models.TextChoices):
+        TEXT = "text", _("text")
+        TEXTAREA = "textarea", _("textarea")
+        NUMBER = "number", _("number")
+        EMAIL = "email", _("email")
+        DATE = "date", _("date")
+        CHOICE = "choice", _("choice")
+        MULTICHOICE = "multichoice", _("multichoice")
+        CHECKBOX = "checkbox", _("checkbox")
+        FILE = "file", _("file")
+
+    form = models.ForeignKey(Form, on_delete=models.CASCADE, related_name="fields", verbose_name=_("form"))
+    key = models.SlugField(_("key"))
+    label = models.CharField(_("label"), max_length=255)
+    field_type = models.CharField(_("field type"), max_length=255, choices=FieldType.choices, default=FieldType.TEXT)
+    required = models.BooleanField(_("required?"), default=True)
+    help_text = models.TextField(_("help text"), blank=True)
+    order = models.PositiveIntegerField(_("order"), default=0)
+    is_active = models.BooleanField(_("is active?"), default=True)
+    options = models.JSONField(_("options"), blank=True, null=True)
+
+    class Meta:
+        verbose_name = _("field")
+        verbose_name_plural = _("fields")
+        ordering = ["form", "order"]
+        constraints = [
+            UniqueConstraint(fields=["form", "key"], name="unique_field_key_per_form"),
+        ]
+
+    def __str__(self):
+        return self.label
+
+
+class Submission(UUIDModel):
+    form = models.ForeignKey(Form, on_delete=models.CASCADE, related_name="submissions", verbose_name=_("form"))
+    member = models.ForeignKey(Member, on_delete=models.SET_NULL, related_name="submissions", verbose_name=_("member"), blank=True, null=True)
+    submitted_at = models.DateTimeField(_("submitted at"), auto_now_add=True)
+
+    class Meta:
+        verbose_name = _("submission")
+        verbose_name_plural = _("submissions")
+        ordering = ["-submitted_at"]
+
+    def __str__(self):
+        return f"{self.form} - {self.member}"
+
+
+class Answer(UUIDModel):
+    submission = models.ForeignKey(Submission, on_delete=models.CASCADE, related_name="answers", verbose_name=_("submission"))
+    field = models.ForeignKey(Field, on_delete=models.PROTECT, related_name="answers", verbose_name=_("field"))
+    value = models.JSONField(_("value"), blank=True, null=True)
+
+    class Meta:
+        verbose_name = _("answer")
+        verbose_name_plural = _("answers")
+        ordering = ["submission", "field"]
+        constraints = [
+            UniqueConstraint(fields=["submission", "field"], name="unique_answer_per_field_per_submission"),
+        ]
+
+    def __str__(self):
+        return f"{self.submission} - {self.field}"