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>

fusion_portal/controllers/portal_main.py

@@ -2507,6 +2507,7 @@ class AuthorizerPortal(CustomerPortal):
                 'client_address_postal': post.get('client_address_postal', '').strip(),
                 'client_phone': post.get('client_phone', '').strip(),
                 'client_email': post.get('client_email', '').strip(),
+                'x_fc_funding_source': post.get('funding_source') or 'direct_private',
                 'notes': post.get('notes', '').strip(),
             }