feat(form-builder): form_field_conditional_logic_{groups,conditions} tables + OrganisationScope cap raise to 5

WS-5c commit 1 of 4 — relational infrastructure for the conditional-
logic tree that replaces form_fields.conditional_logic JSON (ARCH-
FORM-BUILDER §8; addendum Q3 WS-5c).

Tables: groups (nesting via parent_group_id) + conditions (leaves,
value JSON nullable for empty/not_empty). Simple FK to form_fields —
addendum Q3 explicitly excludes form_field_library from conditional_
logic scope, so no polymorphic morph here.

OrganisationScope cap raised 3 → 5 hops. The conditions chain is
4 hops (condition → group → field → schema → organisation_id column)
and the new cap gives headroom for future deeper trees without
denormalising form_field_id onto conditions.

Cascade observer (FormFieldChildTablesCascadeObserver) extended to
physically delete the new groups table on FormField delete (hard or
soft). Conditions cascade automatically via the group_id FK on the
groups table.

Factories: FormFieldConditionalLogicGroupFactory, FormFieldConditional
LogicConditionFactory, and FormFieldFactory::withConditionalLogic($tree)
for concise test fixtures.

Tests: 16 new under tests/Feature/FormBuilder/ConditionalLogic/
(relation, scope, cascade, enum catalogue). 3 new scope-cap tests in
ScopeLeakageTest verify 4/5-hop chains pass and 6-hop throws. Hardcoded
rollback step counts in WS-5a/b migration tests bumped for the 2 new
WS-5c migrations. Baseline 1104 → 1122 green (2988 → 3032 assertions).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Models/Scopes/OrganisationScope.php

@@ -26,9 +26,15 @@ use Illuminate\Database\Eloquent\Scope;
  *         ['column' => 'organisation_id']  — direct scope column, OR
  *         ['via' => ParentModel::class, 'fk' => 'parent_id']  — walk to parent
  *       The resolver recurses through parents until it hits a column strategy
- *       or the legacy $organisationScopeColumn bridge. Cap at 3 hops; deeper
+ *       or the legacy $organisationScopeColumn bridge. Cap at 5 hops; deeper
  *       chains raise TenantScopeResolutionException.
  *
+ *       Cap raised from 3 to 5 in WS-5c (2026-04-26). Legitimate relational
+ *       trees — `form_field_conditional_logic_conditions → group → field →
+ *       schema → org` — exceed the original limit. Raising to 5 accommodates
+ *       this without denormalising `form_field_id` onto conditions (which
+ *       would introduce drift risk).
+ *
  *   (b) Legacy column property (pre-addendum — still supported so Person,
  *       Event, FestivalSection, etc. need not migrate in this work package):
  *       `public string $organisationScopeColumn = 'organisation_id'
@@ -43,7 +49,7 @@ use Illuminate\Database\Eloquent\Scope;
  */
 final class OrganisationScope implements Scope
 {
-    private const MAX_CHAIN_HOPS = 3;
+    private const MAX_CHAIN_HOPS = 5;
 
     public function __construct(
         private readonly ?string $organisationId = null,