feat(backend,docker,docs): implement Go/Gin/SQLite REST API server, Docker containerization, and architecture specifications

- Implement standalone Go backend API server using Gin and pure-Go SQLite (modernc.org/sqlite)
- Add 11-table schema DDL migrations (000001_init.up.sql) based on DATA_TABLE.md
- Add seed data ingestion tool (cmd/seed) and static TypeScript content exporter (cmd/export-content)
- Add configuration loader (internal/config) supporting environment variables and .env files (HOST, PORT, DB_PATH, GIN_MODE, CORS_ALLOW_ORIGINS, AUTO_MIGRATE)
- Add lightweight multi-stage Dockerfile and docker-compose.yml with persistent SQLite volume
- Add comprehensive architecture specification (ARCHITECTURE.md) and REST API interface specification (API_INTERFACE.md)
- Harmonize frontend publications page to consume isHighlight flag from database-synced content

backend/internal/models/lectures.go

@@ -0,0 +1,24 @@
+package models
+
+type Course struct {
+	ID           int     `json:"id"`
+	SemesterID   int     `json:"semester_id"`
+	Code         string  `json:"code"`
+	NameEn       string  `json:"name_en"`
+	NameKr       *string `json:"name_kr,omitempty"`
+	Note         *string `json:"note,omitempty"`
+	DisplayOrder int     `json:"display_order"`
+}
+
+type Semester struct {
+	ID   int    `json:"id"`
+	Year int    `json:"year"`
+	Term string `json:"term"`
+}
+
+type SemesterWithCourses struct {
+	ID      int      `json:"id"`
+	Year    int      `json:"year"`
+	Term    string   `json:"term"`
+	Courses []Course `json:"courses"`
+}