Add initial backend implementation

- Go module with Gin, GORM, JWT, excelize dependencies
- Configuration loading from YAML with all settings
- GORM models for users, categories, components, configurations, alerts
- Repository layer for all entities
- Services: auth (JWT), pricing (median/average/weighted), components,
  quotes, configurations, export (CSV/XLSX), alerts
- Middleware: JWT auth, role-based access, CORS
- HTTP handlers for all API endpoints
- Main server with dependency injection and graceful shutdown

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/handlers/configuration.go

@@ -0,0 +1,156 @@
+package handlers
+
+import (
+	"io"
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+	"github.com/mchus/quoteforge/internal/middleware"
+	"github.com/mchus/quoteforge/internal/services"
+)
+
+type ConfigurationHandler struct {
+	configService *services.ConfigurationService
+	exportService *services.ExportService
+}
+
+func NewConfigurationHandler(
+	configService *services.ConfigurationService,
+	exportService *services.ExportService,
+) *ConfigurationHandler {
+	return &ConfigurationHandler{
+		configService: configService,
+		exportService: exportService,
+	}
+}
+
+func (h *ConfigurationHandler) List(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+	page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
+	perPage, _ := strconv.Atoi(c.DefaultQuery("per_page", "20"))
+
+	configs, total, err := h.configService.ListByUser(userID, page, perPage)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"configurations": configs,
+		"total":          total,
+		"page":           page,
+		"per_page":       perPage,
+	})
+}
+
+func (h *ConfigurationHandler) Create(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+
+	var req services.CreateConfigRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	config, err := h.configService.Create(userID, &req)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusCreated, config)
+}
+
+func (h *ConfigurationHandler) Get(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+	uuid := c.Param("uuid")
+
+	config, err := h.configService.GetByUUID(uuid, userID)
+	if err != nil {
+		status := http.StatusNotFound
+		if err == services.ErrConfigForbidden {
+			status = http.StatusForbidden
+		}
+		c.JSON(status, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, config)
+}
+
+func (h *ConfigurationHandler) Update(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+	uuid := c.Param("uuid")
+
+	var req services.CreateConfigRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	config, err := h.configService.Update(uuid, userID, &req)
+	if err != nil {
+		status := http.StatusInternalServerError
+		if err == services.ErrConfigNotFound {
+			status = http.StatusNotFound
+		} else if err == services.ErrConfigForbidden {
+			status = http.StatusForbidden
+		}
+		c.JSON(status, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, config)
+}
+
+func (h *ConfigurationHandler) Delete(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+	uuid := c.Param("uuid")
+
+	err := h.configService.Delete(uuid, userID)
+	if err != nil {
+		status := http.StatusInternalServerError
+		if err == services.ErrConfigNotFound {
+			status = http.StatusNotFound
+		} else if err == services.ErrConfigForbidden {
+			status = http.StatusForbidden
+		}
+		c.JSON(status, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"message": "deleted"})
+}
+
+func (h *ConfigurationHandler) ExportJSON(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+	uuid := c.Param("uuid")
+
+	data, err := h.configService.ExportJSON(uuid, userID)
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.Header("Content-Disposition", "attachment; filename=config.json")
+	c.Data(http.StatusOK, "application/json", data)
+}
+
+func (h *ConfigurationHandler) ImportJSON(c *gin.Context) {
+	userID := middleware.GetUserID(c)
+
+	data, err := io.ReadAll(c.Request.Body)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "failed to read body"})
+		return
+	}
+
+	config, err := h.configService.ImportJSON(userID, data)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusCreated, config)
+}