I work on an image search engine[0], main idea has been to preserve all the original meta-data and directory structure while allowing semantic and meta-data search from a single interface. All meta-data is stored in a single json file, with original Path and filenames, in case ever to create backups. Instead of uploading photos to a server, you could host it on a cheap VPS with enough space, and instead Index there. (by default it a local app). It is an engine though and don't provide any Auth or specific features like sharing albums!

[0] https://github.com/eagledot/hachi