feat: grouping phase 1 — schema, ungrouped tab, time-window grouping, hash verification

Schema:
- Add GroupingSource enum (ALBUM, MANUAL, AUTO_TIME, AUTO_PATTERN, etc.)
- Add groupingSource field to PackageGroup with backfill
- Add SystemNotification model for persistent alerts
- Add NotificationType and NotificationSeverity enums

Ungrouped staging tab:
- Add listUngroupedPackages/countUngroupedPackages queries
- Add "Ungrouped" tab to STL page showing packages without a group

Time-window auto-grouping:
- After album grouping, cluster ungrouped packages within configurable
  time window (default 5 min, AUTO_GROUP_TIME_WINDOW_MINUTES env var)
- Groups named from common filename prefix
- Groups created with groupingSource=AUTO_TIME

Hash verification after split:
- Re-hash split parts and compare to original contentHash
- Log error and create SystemNotification on mismatch
- Prevents silently corrupted split uploads

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prisma/migrations/20260330120000_grouping_and_notifications/migration.sql

@@ -0,0 +1,32 @@
+-- CreateEnum GroupingSource
+CREATE TYPE "GroupingSource" AS ENUM ('ALBUM', 'MANUAL', 'AUTO_TIME', 'AUTO_PATTERN', 'AUTO_REPLY', 'AUTO_ZIP', 'AUTO_CAPTION');
+
+-- CreateEnum NotificationType
+CREATE TYPE "NotificationType" AS ENUM ('HASH_MISMATCH', 'MISSING_PART', 'UPLOAD_FAILED', 'DOWNLOAD_FAILED', 'GROUPING_CONFLICT', 'INTEGRITY_AUDIT');
+
+-- CreateEnum NotificationSeverity
+CREATE TYPE "NotificationSeverity" AS ENUM ('INFO', 'WARNING', 'ERROR');
+
+-- AlterTable: add groupingSource to package_groups
+ALTER TABLE "package_groups" ADD COLUMN "groupingSource" "GroupingSource" NOT NULL DEFAULT 'MANUAL';
+
+-- Backfill: mark album-based groups
+UPDATE "package_groups" SET "groupingSource" = 'ALBUM' WHERE "mediaAlbumId" IS NOT NULL;
+
+-- CreateTable: system_notifications
+CREATE TABLE "system_notifications" (
+    "id" TEXT NOT NULL,
+    "type" "NotificationType" NOT NULL,
+    "severity" "NotificationSeverity" NOT NULL DEFAULT 'INFO',
+    "title" TEXT NOT NULL,
+    "message" TEXT NOT NULL,
+    "context" JSONB,
+    "isRead" BOOLEAN NOT NULL DEFAULT false,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "system_notifications_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "system_notifications_isRead_createdAt_idx" ON "system_notifications"("isRead", "createdAt");
+CREATE INDEX "system_notifications_type_idx" ON "system_notifications"("type");