feat(fusion_portal): funding-source selector on accessibility forms (#3)

* feat(fusion_portal): funding-source selector on accessibility forms

Reps can now mark an accessibility assessment's funding source on the web form
(Private / March of Dimes / ODSP / WSIB / Hardship / Insurance / Other) so the
generated draft sale order routes to the correct funding pipeline instead of
always defaulting to private pay. Adds Hardship to the x_fc_funding_source
selection + sale_type_map; the new form <select> is auto-serialised by the
existing FormData submit, and accessibility_assessment_save now maps
funding_source -> x_fc_funding_source. The model + SO routing were already in
place (2026-04 audit fix) — this closes the form + controller gap.

Plan: docs/superpowers/plans/2026-06-02-accessibility-funding-selector.md
Spec: docs/superpowers/specs/2026-06-02-assessment-visit-funding-design.md

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(fusion_portal): validate funding_source in accessibility save (parity with booking)

Coerce an unexpected/tampered funding_source to direct_private instead of passing
it raw into create() (which would raise on the Selection field). Mirrors the
/book-assessment controller; the whitelist is derived from the model selection so
it auto-covers hardship and any future values.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_portal/models/accessibility_assessment.py

@@ -73,6 +73,7 @@ class FusionAccessibilityAssessment(models.Model):
             ('march_of_dimes', 'March of Dimes'),
             ('odsp', 'ODSP'),
             ('wsib', 'WSIB'),
+            ('hardship', 'Hardship Funding'),
             ('insurance', 'Private Insurance'),
             ('direct_private', 'Private Pay (Direct)'),
             ('other', 'Other'),
@@ -772,6 +773,7 @@ class FusionAccessibilityAssessment(models.Model):
             'march_of_dimes': 'march_of_dimes',
             'odsp': 'odsp',
             'wsib': 'wsib',
+            'hardship': 'hardship',
             'insurance': 'insurance',
             'direct_private': 'direct_private',
             'other': 'other',