Phase 2+5: lab submissions and student lab flow

- progress: submissions table+V4; SubmissionService (deadline-gated submit,
  unlimited resubmits, per-student history, zip download); files on disk
  data/submissions/{student}/{lab}/{seq}/
- student API: POST submit (multipart), GET me submissions, download; admin
  GET lab submissions + admin download (zip pack)
- progress enrich(): labId in MeAssignment; web DTO aligned
- web: /student dashboard (avg/best/worst cards), /student/labs cards,
  /student/labs/{id}: condition md, variant block, submit form, history;
  'Лабораторные' link in nav for students
- admin: submissions column on lab assignment table + download link
- fixed long-standing template bug: broken @{} expression (missing }) in
  admin/lab and student/lab

services/gateway/src/main/resources/application.yml

@@ -20,7 +20,7 @@ spring:
             - id: progress
               uri: ${LMS_PROGRESS_URI:http://localhost:8083}
               predicates:
-                - Path=/api/v1/assign,/api/v1/assign/**,/api/v1/assignments/**,/api/v1/levels,/api/v1/levels/**,/api/v1/me/**,/api/v1/distribute,/api/v1/distribute/**,/api/v1/grades,/api/v1/grades/**
+                - Path=/api/v1/assign,/api/v1/assign/**,/api/v1/assignments/**,/api/v1/levels,/api/v1/levels/**,/api/v1/me/**,/api/v1/distribute,/api/v1/distribute/**,/api/v1/grades,/api/v1/grades/**,/api/v1/submissions/**
 
 management:
   endpoints: