Add deal co-assignees and saved filters on people/pipeline lists.

Deals keep a primary owner plus shared assignees with matching visibility; Contacts and Pipeline can save and reuse filter presets.

apps/api/prisma/migrations/20260927150000_deal_assignees/migration.sql

@@ -0,0 +1,16 @@
+-- CreateTable
+CREATE TABLE "_DealAssignees" (
+    "A" TEXT NOT NULL,
+    "B" TEXT NOT NULL,
+
+    CONSTRAINT "_DealAssignees_AB_pkey" PRIMARY KEY ("A","B")
+);
+
+-- CreateIndex
+CREATE INDEX "_DealAssignees_B_index" ON "_DealAssignees"("B");
+
+-- AddForeignKey
+ALTER TABLE "_DealAssignees" ADD CONSTRAINT "_DealAssignees_A_fkey" FOREIGN KEY ("A") REFERENCES "Deal"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "_DealAssignees" ADD CONSTRAINT "_DealAssignees_B_fkey" FOREIGN KEY ("B") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;