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/standardization.go

@@ -0,0 +1,39 @@
+package models
+
+type StandardDocument struct {
+	ID          int     `json:"id"`
+	BodyID      int     `json:"body_id"`
+	WG          string  `json:"wg"`
+	ProjectName string  `json:"project_name"`
+	Title       string  `json:"title"`
+	DocRef      string  `json:"doc_ref"`
+	Status      string  `json:"status"`
+	PublishedAt *string `json:"published_at,omitempty"`
+}
+
+type StandardProjectGroup struct {
+	WG        string             `json:"wg"`
+	Name      string             `json:"name"`
+	Documents []StandardDocument `json:"documents"`
+}
+
+type StandardsBody struct {
+	ID           int     `json:"id"`
+	Org          string  `json:"org"`
+	FullName     string  `json:"full_name"`
+	Scope        string  `json:"scope"`
+	Period       string  `json:"period"`
+	Role         *string `json:"role,omitempty"`
+	DisplayOrder int     `json:"display_order"`
+}
+
+type StandardsBodyWithProjects struct {
+	ID           int                    `json:"id"`
+	Org          string                 `json:"org"`
+	FullName     string                 `json:"full_name"`
+	Scope        string                 `json:"scope"`
+	Period       string                 `json:"period"`
+	Role         *string                `json:"role,omitempty"`
+	DisplayOrder int                    `json:"display_order"`
+	Projects     []StandardProjectGroup `json:"projects"`
+}