Switch from net/http to gin-gonic web framework

- Added gin-gonic v1.10.0 dependency
- Refactored router.go: clean route groups with middleware chains
- Refactored all handlers to use gin.Context instead of http.ResponseWriter/*http.Request
- Simplified response helpers (JSON, Error, Success, Created, NoContent)
- Clean auth middleware using Gin's c.Set() for context
- Cleaner route definitions with path parameters (e.g., /domains/:name/users/:id)
- Admin routes moved to /api/admin group with RequireAdmin middleware

backend/internal/api/handlers/logs.go

@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"strconv"
 
+	"github.com/gin-gonic/gin"
 	"github.com/imc-vibe/backend/internal/mail"
 )
 
@@ -13,26 +14,21 @@ func NewLogsHandler() *LogsHandler {
 	return &LogsHandler{}
 }
 
-func (h *LogsHandler) List(w http.ResponseWriter, r *http.Request) {
-	if r.Method != http.MethodGet {
-		Error(w, http.StatusMethodNotAllowed, "method not allowed")
-		return
-	}
-
+func (h *LogsHandler) List(c *gin.Context) {
 	hours := 1
-	if h := r.URL.Query().Get("hours"); h != "" {
+	if h := c.Query("hours"); h != "" {
 		if n, err := strconv.Atoi(h); err == nil && n > 0 {
 			hours = n
 		}
 	}
 
-	filter := r.URL.Query().Get("filter")
+	filter := c.Query("filter")
 
 	entries, err := mail.GetLogs(hours, filter)
 	if err != nil {
-		Error(w, http.StatusServiceUnavailable, "log service not available")
+		Error(c, http.StatusServiceUnavailable, "log service not available")
 		return
 	}
 
-	Success(w, entries)
+	Success(c, entries)
 }