feat(api): implement exam and grade synchronization modules

Add new functionality for managing and synchronizing academic grades and exam schedules. This includes new models, repositories, services, and HTTP handlers, along with updated gRPC definitions and dependency injection configuration.

Additionally, improve the reliability of unread message count tracking by implementing an atomic Lua script for Redis operations in the conversation cache.

internal/model/exam.go

@@ -0,0 +1,28 @@
+package model
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+)
+
+type Exam struct {
+	ID         string `json:"id" gorm:"type:varchar(36);primaryKey"`
+	UserID     string `json:"user_id" gorm:"type:varchar(36);index;not null"`
+	Semester   string `json:"semester" gorm:"type:varchar(30);not null"`
+	CourseName string `json:"course_name" gorm:"type:varchar(120);not null"`
+	ExamType   string `json:"exam_type" gorm:"type:varchar(30)"`
+	Date       string `json:"date" gorm:"type:varchar(20)"`
+	Time       string `json:"time" gorm:"type:varchar(30)"`
+	Week       string `json:"week" gorm:"type:varchar(20)"`
+	Weekday    string `json:"weekday" gorm:"type:varchar(10)"`
+	CreatedAt  time.Time
+	UpdatedAt  time.Time
+}
+
+func (e *Exam) BeforeCreate(tx *gorm.DB) error {
+	SetUUIDIfEmpty(&e.ID)
+	return nil
+}
+
+func (Exam) TableName() string { return "exams" }