fix(contacts): allow deletion — SET NULL on broadcast_recipients, deals

Root cause (error 23503):
  broadcast_recipients.contact_id and deals.contact_id were declared
  NOT NULL REFERENCES contacts(id) with no ON DELETE clause, so
  Postgres defaulted to NO ACTION. Any contact who'd ever received a
  broadcast or been attached to a deal became un-deletable with
  "violates foreign key constraint broadcast_recipients_contact_id_fkey".

Fix (migration 004):
  Relax both FKs to ON DELETE SET NULL + drop NOT NULL on both
  columns. History rows survive with contact_id = NULL. The UI is
  already null-safe:
    - broadcast detail:  contact?.name ?? 'Unknown'
    - deal card:         contact?.name || contact?.phone || 'No contact'
    - CSV export:        contact?.name ?? ''

Why not CASCADE:
  CASCADE would wipe broadcast recipient rows and trigger the
  aggregate recount on broadcasts (migration 003), retroactively
  changing sent_count / delivered_count / read_count. It would also
  delete deal history. SET NULL preserves both counts and history.

Type/code:
  - Deal.contact_id + BroadcastRecipient.contact_id widen to
    string | null
  - DealForm: setContactId(deal.contact_id ?? "") — the contact
    picker uses "" to mean unselected

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

src/components/pipelines/deal-form.tsx

@@ -79,7 +79,9 @@ export function DealForm({
       setTitle(deal.title);
       setValue(String(deal.value ?? ""));
       setCurrency(deal.currency || "USD");
-      setContactId(deal.contact_id);
+      // contact_id is nullable when the contact has been deleted
+      // (migration 004: ON DELETE SET NULL). "" means "no selection".
+      setContactId(deal.contact_id ?? "");
       setStageId(deal.stage_id);
       setAssignedTo(deal.assigned_to ?? "");
       setExpectedCloseDate(deal.expected_close_date ?? "");

src/types/index.ts

@@ -141,7 +141,11 @@ export interface Deal {
   user_id: string;
   pipeline_id: string;
   stage_id: string;
-  contact_id: string;
+  /**
+   * Nullable after migration 004 — becomes NULL when the referenced
+   * contact is deleted (ON DELETE SET NULL). History preserved.
+   */
+  contact_id: string | null;
   conversation_id?: string;
   assigned_to?: string;
   title: string;
@@ -182,7 +186,12 @@ export interface Broadcast {
 export interface BroadcastRecipient {
   id: string;
   broadcast_id: string;
-  contact_id: string;
+  /**
+   * Nullable after migration 004 — becomes NULL when the referenced
+   * contact is deleted (ON DELETE SET NULL). History preserved; the
+   * UI renders "Unknown" for orphaned rows.
+   */
+  contact_id: string | null;
   status: RecipientStatus;
   sent_at?: string;
   delivered_at?: string;

supabase/migrations/004_contact_delete_set_null.sql

@@ -0,0 +1,65 @@
+-- ============================================================
+-- Allow contact deletion without wiping history.
+--
+-- broadcast_recipients.contact_id and deals.contact_id were declared
+-- NOT NULL REFERENCES contacts(id) with no ON DELETE action, so
+-- Postgres defaults to NO ACTION. The first time a user tried to
+-- delete a contact that had ever received a broadcast or been
+-- attached to a deal, the delete failed with:
+--
+--   ERROR 23503: update or delete on table "contacts" violates
+--   foreign key constraint ... on table <other>
+--
+-- CASCADE is the wrong fix — it would silently wipe historical
+-- broadcast recipient rows (breaking audit + retroactively moving
+-- broadcasts.sent_count / delivered_count / read_count etc. via the
+-- aggregate trigger) and deal rows.
+--
+-- SET NULL is the right fix: history rows survive with a NULL
+-- contact_id. The UI is already null-safe (contact?.name ?? 'Unknown',
+-- contact?.phone, etc.).
+--
+-- Idempotent — safe to run multiple times.
+-- ============================================================
+
+-- ── broadcast_recipients.contact_id ────────────────────────────
+ALTER TABLE broadcast_recipients
+  ALTER COLUMN contact_id DROP NOT NULL;
+
+DO $$
+BEGIN
+  IF EXISTS (
+    SELECT 1 FROM pg_constraint
+    WHERE conname = 'broadcast_recipients_contact_id_fkey'
+      AND conrelid = 'broadcast_recipients'::regclass
+  ) THEN
+    ALTER TABLE broadcast_recipients
+      DROP CONSTRAINT broadcast_recipients_contact_id_fkey;
+  END IF;
+END $$;
+
+ALTER TABLE broadcast_recipients
+  ADD CONSTRAINT broadcast_recipients_contact_id_fkey
+    FOREIGN KEY (contact_id) REFERENCES contacts(id)
+    ON DELETE SET NULL;
+
+-- ── deals.contact_id ───────────────────────────────────────────
+ALTER TABLE deals
+  ALTER COLUMN contact_id DROP NOT NULL;
+
+DO $$
+BEGIN
+  IF EXISTS (
+    SELECT 1 FROM pg_constraint
+    WHERE conname = 'deals_contact_id_fkey'
+      AND conrelid = 'deals'::regclass
+  ) THEN
+    ALTER TABLE deals
+      DROP CONSTRAINT deals_contact_id_fkey;
+  END IF;
+END $$;
+
+ALTER TABLE deals
+  ADD CONSTRAINT deals_contact_id_fkey
+    FOREIGN KEY (contact_id) REFERENCES contacts(id)
+    ON DELETE SET NULL;