feat(api): add API documentation and ShareX integration

- Add an API documentation page with curl and ShareX examples.
- Implement a dynamic ShareX configuration endpoint (`/api/v1/sharex/warpbox-anonymous.sxcu`) that generates a `.sxcu` file pre-configured with the instance's base URL.
- Update anonymous uploads to return a private management link (`manageUrl`) and a deletion link (`deleteUrl`) in JSON responses.
- Update README with details on Stage 3 Anonymous Integrations.
- Add styling for the new API documentation view and management details.

backend/libs/handlers/upload.go

@@ -2,10 +2,14 @@ package handlers
 
 import (
 	"errors"
+	"fmt"
+	"mime/multipart"
 	"net/http"
 	"strconv"
+	"strings"
 
 	"warpbox.dev/backend/libs/helpers"
+	"warpbox.dev/backend/libs/jobs"
 	"warpbox.dev/backend/libs/services"
 )
 
@@ -16,7 +20,7 @@ func (a *App) Upload(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	files := r.MultipartForm.File["file"]
+	files := uploadFiles(r)
 	result, err := a.uploadService.CreateBox(files, services.UploadOptions{
 		MaxDays:           parseInt(r.FormValue("max_days")),
 		MaxDownloads:      parseInt(r.FormValue("max_downloads")),
@@ -28,8 +32,16 @@ func (a *App) Upload(w http.ResponseWriter, r *http.Request) {
 		helpers.WriteJSONError(w, http.StatusBadRequest, err.Error())
 		return
 	}
+	jobs.GenerateThumbnailsForBoxAsync(a.uploadService, a.logger, result.BoxID)
 
-	helpers.WriteJSON(w, http.StatusCreated, result)
+	if wantsJSON(r) {
+		helpers.WriteJSON(w, http.StatusCreated, result)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.WriteHeader(http.StatusCreated)
+	_, _ = fmt.Fprintln(w, result.BoxURL)
 }
 
 func parseInt(value string) int {
@@ -49,3 +61,17 @@ func statusForDownloadError(err error) int {
 	}
 	return http.StatusForbidden
 }
+
+func uploadFiles(r *http.Request) []*multipart.FileHeader {
+	if r.MultipartForm == nil {
+		return nil
+	}
+	files := make([]*multipart.FileHeader, 0)
+	files = append(files, r.MultipartForm.File["file"]...)
+	files = append(files, r.MultipartForm.File["sharex"]...)
+	return files
+}
+
+func wantsJSON(r *http.Request) bool {
+	return strings.Contains(strings.ToLower(r.Header.Get("Accept")), "application/json")
+}