Lab assignment management UI and student variant view

- progress-service: POST /api/v1/assign (manual variant), GET /api/v1/assignments?labId=
  (enriched assignments), fixed enrich() to return real variant number/title/statement
- gateway: routes for /api/v1/assign and /api/v1/levels (exact paths)
- web: lab detail page shows students grouped with level and variant selects,
  group filter, distribute/redistribute buttons, source badge (auto/manual)
- web: student dashboard renders variant statement via libs/markdown (spoilers,
  code highlight, sanitized)
- academic-service: unquote YAML front-matter values (variant numbers were quoted)
- academic-service: LabLevelDetail.id for level references

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

@@ -144,19 +144,28 @@ class LabImportParser {
         val fm = mutableMapOf<String, String>()
         for (line in fmLines) {
             val parts = line.split(":", limit = 2)
-            if (parts.size == 2) fm[parts[0].trim()] = parts[1].trim()
+            if (parts.size == 2) fm[parts[0].trim()] = unquote(parts[1].trim())
         }
         val levelCode = normalizeLevel(fm["level"] ?: "basic")
         if (levelMap[levelCode] == null) return null
         val body = lines.drop(secondSep + 1).joinToString("\n").trim()
         return VariantMeta(
             level = levelCode,
-            number = fm["number"] ?: return null,
+            number = fm["number"]?.takeIf { it.isNotBlank() } ?: return null,
             title = fm["title"] ?: "",
             statement = body.ifBlank { "—" },
         )
     }
 
+    private fun unquote(value: String): String =
+        if (value.length >= 2 &&
+            ((value.first() == '"' && value.last() == '"') || (value.first() == '\'' && value.last() == '\''))
+        ) {
+            value.substring(1, value.length - 1)
+        } else {
+            value
+        }
+
     private fun normalizeLevel(s: String): String = when (s.lowercase().trim()) {
         "main", "basic", "обычная", "основная" -> "basic"
         "advanced", "повышенная", "повышенной", "hard" -> "advanced"