Add file visibility (PRIVATE/PUBLIC) + public files API

Adds a visibility enum to files with PRIVATE (default) and PUBLIC states.
PUBLIC files are accessible via an unauthenticated /api/files/v1/{fileID}
endpoint that redirects to a presigned S3 URL. Introduces pkg/file service
to manage file operations. Logo uploads (trust centers, organizations,
frameworks, references) are marked PUBLIC; other files are PRIVATE.
Includes database migration and backfill for existing logos.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/server/api/files/v1/handler.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package files_v1
+
+import (
+	"errors"
+	"net/http"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"go.gearno.de/kit/log"
+	"go.probo.inc/probo/pkg/coredata"
+	"go.probo.inc/probo/pkg/gid"
+	"go.probo.inc/probo/pkg/file"
+)
+
+const presignedURLExpiry = 1 * time.Hour
+
+type Handler struct {
+	logger  *log.Logger
+	fileSvc *file.Service
+}
+
+func NewMux(logger *log.Logger, fileSvc *file.Service) *chi.Mux {
+	h := &Handler{
+		logger:  logger,
+		fileSvc: fileSvc,
+	}
+
+	r := chi.NewRouter()
+
+	r.Get("/{fileID}", h.handleGetPublicFile)
+
+	return r
+}
+
+func (h *Handler) handleGetPublicFile(w http.ResponseWriter, r *http.Request) {
+	fileIDStr := chi.URLParam(r, "fileID")
+
+	fileID, err := gid.ParseGID(fileIDStr)
+	if err != nil {
+		http.NotFound(w, r)
+		return
+	}
+
+	presignedURL, err := h.fileSvc.GetPublicFileURL(r.Context(), fileID, presignedURLExpiry)
+	if err != nil {
+		if errors.Is(err, coredata.ErrResourceNotFound) {
+			http.NotFound(w, r)
+			return
+		}
+
+		h.logger.ErrorCtx(
+			r.Context(),
+			"cannot get public file URL",
+			log.Error(err),
+			log.String("file_id", fileIDStr),
+		)
+		http.Error(w, "internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	http.Redirect(w, r, presignedURL, http.StatusTemporaryRedirect)
+}