I want an app that runs locally on my phone in my pocket and indexes the photos I've stored locally there, without ever needing any kind of network connection.
But the way you're describing your setup, it seems to me as if copying your photos to your computer in order to get them indexed is a necessary step.
While this seems very interesting, it doesn't seem to exist as an app, the download page only lists downloads for desktop operating systems:
https://www.digikam.org/download/
Do they also provide an app somewhere where I haven't looked yet?
All hosted and processed on my local computer, and connected to the mobile app
The way you write this makes it seem as if the app doesn't actually locally index locally stored photos. Is that so?
Watching other people play sports.
I really want an app that locally indexes my locally stored photos and lets me search them locally, based on places, things or people seen in the photo.
Ink runs when dragged over by a right handed writer moving left.
No ink will run as long as you hold your ink brush correctly, see this video for a demonstration of traditional Japanese handwriting, top to bottom, right to left, brush held comfortably by a right handed writer, no ink dragged over:
That all depends on what you actually mean by "no other proximate reason".
I think we all agree that the police should take immediate action if someone is driving the wrong direction against traffic, even if they're doing nothing else wrong and are driving the posted speed limit, to take an absolutely obvious example.
The argument can literally be made that you’re driving dangerously no matter how fast you go.
Well, that's certainly true also in every jurisdiction I'm familiar with, as it should be, common sense, really.
Where I live there are only upper speed limits on most roads except highways. On other roads you can drive as slowly as you want,
Are you sure that you really don't have any traffic rules against causing a hazard or impeding traffic flow by being too slow? That seems both unusual and unsafe to me.
There are speed limits in both directions, in every jurisdiction I'm familiar with it's illegal to drive both too fast and too slow, to exceed the posted speed limit or to drive so slowly that it impedes other traffic.
It's a conspiracy.
Well, that's exactly why such an app was what I wrote as my reply to the question "What app/program do you wish existed […]?"