feat: rename service to galo, add halo branding and release build

- rename Go module, binary, systemd unit, PG_DATABASE default, frontend package and docs from shared-album to galo
- add theme-aware halo emblem and favicon (new ui-branding capability)
- add make build-release (versioned, stripped, static binary) and run the binary from the repo root

backend/internal/photos/handlers.go

@@ -9,8 +9,8 @@ import (
 
 	"github.com/gin-gonic/gin"
 
-	"shared-album/internal/auth"
-	"shared-album/internal/httpx"
+	"galo/internal/auth"
+	"galo/internal/httpx"
 )
 
 const maxUploadSize = 100 << 20