Phase 1 fixes: broken dialogs, score width, status badge, MSK date round-trip

- group/lab/labs: move dialogs/scripts INSIDE the #content fragment (they were
  outside — the layout fragment dropped them, which is why 'add student' did nothing)
- group.html toast had swallowed the dialog (th:if createdStudent) — split properly
- .input-score width no longer overridden by .inline-form .input-sm (10rem min)
- lab page: remove separate 'change status' button — status badge is now a toggle
  button itself (confirm dialog kept)
- DateUtils.localInput/toUtcIso: dates entered in datetime-local are Moscow-local,
  stored as UTC instant, shown back MSK — correct round-trip both ways
- academic parseInstant: naive local datetimes treated as Europe/Moscow
- README/module docs left as-is

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

@@ -17,7 +17,7 @@ import java.math.BigDecimal
 import java.time.Instant
 import java.time.LocalDateTime
 import java.time.OffsetDateTime
-import java.time.ZoneOffset
+import java.time.ZoneId
 import java.util.UUID
 
 @Service
@@ -291,7 +291,7 @@ class LabService(
         val v = value?.takeIf { it.isNotBlank() } ?: return null
         return runCatching { Instant.parse(v) }
             .recoverCatching { OffsetDateTime.parse(v).toInstant() }
-            .recoverCatching { LocalDateTime.parse(v).atOffset(ZoneOffset.UTC).toInstant() }
+            .recoverCatching { LocalDateTime.parse(v).atZone(ZoneId.of("Europe/Moscow")).toInstant() }
             .getOrNull()
     }
 }