feat: general lab comment and strict square UI

Add a non-required general comment for a student's lab grade (progress V9, API, admin modal, student card). Empty string is the default. Switch the UI to square corners and bump static asset versions.

docs/03-domain-model.md

@@ -269,6 +269,7 @@ classDiagram
         +UUID studentId
         +UUID labId
         +BigDecimal score
+        +String generalComment
         +Instant updatedAt
     }
     class GradePublication {
@@ -635,6 +636,7 @@ erDiagram
         uuid student_id PK
         uuid lab_id PK
         numeric score
+        text general_comment
         timestamptz updated_at
     }
     GRADE_PUBLICATIONS {