add index clearing, cleanup

fix chunk access by ID in sqlite backend

fix access of sources

firs go at abrstracting the storage backend and using sqlite

Requires the dev branch of the sqlite plugin

added info method for kd tree inspection

Faster (and cheaper) reindexing

We can reuse the previous data if the page hasn't changed

More robustness in creating the index

Retry failed API connections, do not abort the whole indexing and rather
skip a chunk. CLI testing tool for the split mechanism

don't index hidden pages

fix logging in CLI mode

added fullscreen mode

german translation and more styling adjustments

Check ACLs before using sources

some more doc blocks

pin php to 8.1

Frontend integration with simple syntax component

support chatting

asking standalone question works

initial checkin. working vector storage and similarity search