Use stable files API URLs for vendor logo fields

CommonThirdParty.logoUrl and TrustCenterReference.logoUrl were
returning expiring S3 presigned URLs, which break if cached or
shared past their TTL.

Replace with stable /api/files/v1/{id} application URLs.
file.Service now generates these via baseurl; a new filesign
package owns presigning for the files/v1 HTTP handler that
does the internal redirect.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/server/api/api.go

@@ -31,7 +31,7 @@ import (
 	"go.probo.inc/probo/pkg/connector/provider"
 	"go.probo.inc/probo/pkg/cookiebanner"
 	"go.probo.inc/probo/pkg/esign"
-	"go.probo.inc/probo/pkg/file"
+	"go.probo.inc/probo/pkg/filesign"
 	"go.probo.inc/probo/pkg/geoloc"
 	"go.probo.inc/probo/pkg/iam"
 	"go.probo.inc/probo/pkg/mailman"
@@ -55,7 +55,7 @@ type (
 		BaseURL           *baseurl.BaseURL
 		AllowedOrigins    []string
 		Probo             *probo.Service
-		File              *file.Service
+		FileSign          *filesign.Service
 		IAM               *iam.Service
 		Trust             *trust.Service
 		ESign             *esign.Service
@@ -207,7 +207,7 @@ func NewServer(cfg Config) (*Server, error) {
 		),
 		filesHandler: files_v1.NewMux(
 			cfg.Logger.Named("files.v1"),
-			cfg.File,
+			cfg.FileSign,
 		),
 		mcpHandler: mcp_v1.NewMux(
 			cfg.Logger.Named("mcp.v1"),