fix(db): add missing FavoriteLink migration

FavoriteLink existed in schema.prisma but was never captured in a
migration -- same bug class as the DashboardLayout fix in
20260629130000_add_missing_tables. It silently worked in local dev
(table created via db push) but any environment relying on
`prisma migrate deploy` never got the table, causing every
GET /favorites request to 500 with PrismaClientKnownRequestError
P2021 ("table does not exist").

Found live testing the production deploy at alpha.tessera.ctl.de:
adding a Favoriten widget triggered the 500. Confirmed via server
logs (docker logs) and by inspecting _prisma_migrations / \dt on
that database.

CREATE TABLE/INDEX IF NOT EXISTS makes this safe to apply against
environments where the table already exists untracked (verified: ran
clean against local dev's DB, which already had the table from a
prior db push, with zero errors and zero data loss).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/prisma/migrations/20260708090000_add_favorite_link/migration.sql

@@ -0,0 +1,29 @@
+-- CreateTable
+-- FavoriteLink existed in schema.prisma but was never captured in a migration
+-- (created via db push in local dev, same class of bug as the DashboardLayout
+-- fix in 20260629130000_add_missing_tables). IF NOT EXISTS makes this safe to
+-- apply against environments where the table already exists untracked.
+CREATE TABLE IF NOT EXISTS "FavoriteLink" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "tenantId" TEXT NOT NULL,
+    "widgetId" TEXT NOT NULL,
+    "title" TEXT NOT NULL,
+    "url" TEXT NOT NULL,
+    "iconUrl" TEXT,
+    "position" INTEGER NOT NULL DEFAULT 0,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "FavoriteLink_pkey" PRIMARY KEY ("id"),
+    CONSTRAINT "FavoriteLink_widgetId_fkey" FOREIGN KEY ("widgetId") REFERENCES "WidgetInstance"("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+
+-- CreateIndex
+CREATE INDEX IF NOT EXISTS "FavoriteLink_userId_idx" ON "FavoriteLink"("userId");
+
+-- CreateIndex
+CREATE INDEX IF NOT EXISTS "FavoriteLink_tenantId_idx" ON "FavoriteLink"("tenantId");
+
+-- CreateIndex
+CREATE INDEX IF NOT EXISTS "FavoriteLink_widgetId_idx" ON "FavoriteLink"("widgetId");