Complete distribution flow and student UI

- progress-service: Distribute variants (round-robin per lab per level),
  student level assignment, API for levels/assignments
- progress-service: Inter-service clients (academic, identity) via RestClient
- web: Admin lab detail page with distribute/level buttons
- web: Student dashboard shows assigned labs from progress-service
- web: ApiClient methods for labs detail, distribute, levels, me/assignments
- academic-service: Add id to LabLevelDetail DTO for progress-service
- Fix: CSS-only layout, footer at bottom via flex column

services/academic-service/src/main/kotlin/ru/ysu/lms/academic/lab/LabDtos.kt

@@ -67,6 +67,7 @@ data class LabDetail(
 )
 
 data class LabLevelDetail(
+    val id: String = "",
     val code: String,
     val title: String,
     val variants: List<VariantDetail>,

services/academic-service/src/main/kotlin/ru/ysu/lms/academic/lab/LabService.kt

@@ -112,6 +112,7 @@ class LabService(
                 val vs = variantsRepo.findByLabIdOrderByNumber(lab.id)
                     .filter { it.labLevel?.id == level.id }
                 LabLevelDetail(
+                    id = level.id.toString(),
                     code = level.code,
                     title = level.title,
                     variants = vs.map { v ->