feat: per-round advancement selection, email preview, Docker/auth fixes

- Bulk notification dialog: per-round checkboxes (default none selected),
  selected count badge, "Preview Email" button with rendered iframe
- Backend: roundIds filter on sendBulkPassedNotifications, new
  previewAdvancementEmail query
- Docker: add external MinIO network so app container can reach MinIO
- File router: try/catch on getPresignedUrl with descriptive error
- Auth: custom NextAuth logger suppresses CredentialsSignin stack traces

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/server/routers/file.ts

@@ -111,9 +111,18 @@ export const fileRouter = router({
         }
       }
 
-      const url = await getPresignedUrl(input.bucket, input.objectKey, 'GET', 900,
-        input.forDownload ? { downloadFileName: input.fileName || input.objectKey.split('/').pop() || 'download' } : undefined
-      ) // 15 min
+      let url: string
+      try {
+        url = await getPresignedUrl(input.bucket, input.objectKey, 'GET', 900,
+          input.forDownload ? { downloadFileName: input.fileName || input.objectKey.split('/').pop() || 'download' } : undefined
+        ) // 15 min
+      } catch (err) {
+        console.error('[file] getPresignedUrl failed:', input.objectKey, err instanceof Error ? err.message : err)
+        throw new TRPCError({
+          code: 'NOT_FOUND',
+          message: `File not available in storage: ${err instanceof Error ? err.message : 'unknown error'}`,
+        })
+      }
 
       // Log file access
       await logAudit({

src/server/routers/project.ts

@@ -1670,20 +1670,63 @@ export const projectRouter = router({
    * Groups by round, determines next round, sends via batch sender.
    * Skips projects that have already been notified (unless skipAlreadySent=false).
    */
+  previewAdvancementEmail: adminProcedure
+    .input(
+      z.object({
+        roundId: z.string(),
+        customMessage: z.string().optional(),
+        fullCustomBody: z.boolean().default(false),
+      })
+    )
+    .query(async ({ ctx, input }) => {
+      const round = await ctx.prisma.round.findUnique({
+        where: { id: input.roundId },
+        select: {
+          name: true,
+          competitionId: true,
+        },
+      })
+      if (!round) throw new TRPCError({ code: 'NOT_FOUND', message: 'Round not found' })
+
+      const rounds = await ctx.prisma.round.findMany({
+        where: { competitionId: round.competitionId },
+        orderBy: { sortOrder: 'asc' },
+        select: { id: true, name: true },
+      })
+      const idx = rounds.findIndex((r) => r.id === input.roundId)
+      const nextRound = rounds[idx + 1]
+
+      const { getAdvancementNotificationTemplate } = await import('@/lib/email')
+      const template = getAdvancementNotificationTemplate(
+        'Team Lead Name',
+        'Example Project Title',
+        round.name,
+        nextRound?.name ?? 'Next Round',
+        input.customMessage || undefined,
+        undefined,
+        input.fullCustomBody,
+      )
+      return { subject: template.subject, html: template.html }
+    }),
+
   sendBulkPassedNotifications: adminProcedure
     .input(
       z.object({
         customMessage: z.string().optional(),
         fullCustomBody: z.boolean().default(false),
         skipAlreadySent: z.boolean().default(true),
+        roundIds: z.array(z.string()).optional(),
       })
     )
     .mutation(async ({ ctx, input }) => {
-      const { customMessage, fullCustomBody, skipAlreadySent } = input
+      const { customMessage, fullCustomBody, skipAlreadySent, roundIds } = input
 
-      // Find all PASSED project round states
+      // Find all PASSED project round states (optionally filtered by round)
       const passedStates = await ctx.prisma.projectRoundState.findMany({
-        where: { state: 'PASSED' },
+        where: {
+          state: 'PASSED',
+          ...(roundIds && roundIds.length > 0 ? { roundId: { in: roundIds } } : {}),
+        },
         select: {
           projectId: true,
           roundId: true,