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/config/config.go

@@ -0,0 +1,104 @@
+package config
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// Config holds all server configuration derived from environment variables and flags.
+type Config struct {
+	Port             int
+	Host             string
+	DBPath           string
+	GinMode          string
+	CORSAllowOrigins string
+	AutoMigrate      bool
+}
+
+// LoadEnvFile reads a simple .env file if it exists and loads variables into environment without overriding existing ones.
+func LoadEnvFile(filenames ...string) {
+	if len(filenames) == 0 {
+		filenames = []string{".env", "../.env"}
+	}
+
+	for _, filename := range filenames {
+		file, err := os.Open(filename)
+		if err != nil {
+			continue
+		}
+
+		scanner := bufio.NewScanner(file)
+		for scanner.Scan() {
+			line := strings.TrimSpace(scanner.Text())
+			if line == "" || strings.HasPrefix(line, "#") {
+				continue
+			}
+
+			parts := strings.SplitN(line, "=", 2)
+			if len(parts) != 2 {
+				continue
+			}
+
+			key := strings.TrimSpace(parts[0])
+			val := strings.TrimSpace(parts[1])
+			// Strip optional surrounding quotes
+			val = strings.Trim(val, `"'`)
+
+			// Only set if not already present in environment
+			if _, exists := os.LookupEnv(key); !exists {
+				_ = os.Setenv(key, val)
+			}
+		}
+		_ = file.Close()
+	}
+}
+
+// Load reads and parses all configuration settings from the environment.
+func Load() *Config {
+	LoadEnvFile()
+
+	cfg := &Config{
+		Port:             8080,
+		Host:             "0.0.0.0",
+		DBPath:           "anl.db",
+		GinMode:          "release",
+		CORSAllowOrigins: "*",
+		AutoMigrate:      true,
+	}
+
+	if portStr := os.Getenv("PORT"); portStr != "" {
+		if p, err := strconv.Atoi(portStr); err == nil && p > 0 {
+			cfg.Port = p
+		}
+	}
+
+	if hostStr := os.Getenv("HOST"); hostStr != "" {
+		cfg.Host = hostStr
+	}
+
+	if dbPathStr := os.Getenv("DB_PATH"); dbPathStr != "" {
+		cfg.DBPath = dbPathStr
+	}
+
+	if ginModeStr := os.Getenv("GIN_MODE"); ginModeStr != "" {
+		cfg.GinMode = ginModeStr
+	}
+
+	if corsStr := os.Getenv("CORS_ALLOW_ORIGINS"); corsStr != "" {
+		cfg.CORSAllowOrigins = corsStr
+	}
+
+	if autoMigrateStr := os.Getenv("AUTO_MIGRATE"); autoMigrateStr != "" {
+		cfg.AutoMigrate = strings.ToLower(autoMigrateStr) != "false" && autoMigrateStr != "0"
+	}
+
+	return cfg
+}
+
+// Address returns the combined host:port address string.
+func (c *Config) Address() string {
+	return fmt.Sprintf("%s:%d", c.Host, c.Port)
+}