fix(audit-wave-9): unified template token picker with custom-field group

Build a shared <TemplateTokenPicker> that renders the canonical
MERGE_FIELDS catalog grouped by scope, plus a dynamically-fetched
"Custom (port-specific)" group surfaced from /api/v1/admin/custom-fields.
The custom group is filtered to entity types the resolver actually
expands at send time (client/interest/berth - see
mergeCustomFieldValues in document-sends.service).

Wire it into both consumers:
- admin/document-templates/template-form.tsx (replaces TEMPLATE_VARIABLES
  list which had drifted from the canonical catalog)
- admin/sales-email-config-card.tsx (replaces flat alphabetical dump)

Closes custom-fields §B "UI surfacing of {{custom.…}} tokens".

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

docs/BACKLOG.md

@@ -42,7 +42,7 @@ Remaining phases — explicitly back-burnered by the user on 2026-05-07:
 - ✅ **Merge tokens** — `{{custom.<fieldName>}}` validators + resolver shipped 2026-05-08. Tokens expand at template-render time for client/interest/berth contexts via `mergeCustomFieldValues` in `document-sends.service.ts`. Banner updated.
 - **Search index** — DEFERRED as design limitation. Adding GIN coverage requires either joining `custom_field_values` per search (slow at scale) or materializing values into a search_text column on the parent (additive maintenance burden). The amber banner documents this.
 - **Audit diff** — N/A. Custom-field values live in their own table, not as a JSONB blob on the parent entity. The `setValues()` service-layer call already creates its own audit log entry (custom-fields.service.ts:349-358), so changes ARE audited — just separately from the entity-diff.
-- **UI surfacing of `{{custom.…}}` tokens in template-edit pickers** — Open. The token list dialog currently only shows static catalog tokens. Surface per-port custom-field definitions as a dynamic group under "Custom" so reps can browse them. Backend already accepts the tokens; this is a UI follow-up.
+- ✅ **UI surfacing of `{{custom.…}}` tokens in template-edit pickers** — landed 2026-05-13. Shared `<TemplateTokenPicker>` (`src/components/admin/shared/template-token-picker.tsx`) renders the canonical `MERGE_FIELDS` catalog grouped by scope plus a dynamically-fetched "Custom (port-specific)" group filtered to entityTypes resolvable at send-time (client/interest/berth). Wired into both `sales-email-config-card.tsx` and `document-templates/template-form.tsx` so both pickers share the same surface.
 
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