Add font selector; load all fonts from fonts/ directory; bump to 0.85

All .ttf files in fonts/ are loaded at startup. The web form now has a
font selector dropdown. Glyph-rendering helpers that previously used
module-level font globals now accept a _FontData parameter threaded
through from generate_svg().

Dockerfile updated to copy all of fonts/ into the image rather than a
single hardcoded .ttf path.

README.md

@@ -40,7 +40,7 @@ source .venv/bin/activate
 cd web && python app.py      # http://localhost:5000
 ```
 
-The font must be installed at `/usr/local/share/fonts/г/ГОСТ_тип_А.ttf`.
+Fonts are loaded at startup from the `fonts/` directory in the repo root.
 
 ### Form parameters
 
@@ -84,13 +84,12 @@ Constructs nest: `{m/s^2}` is a fraction with a superscript in the denominator,
 ## Container
 
 ```bash
-# Copy the font first (not redistributed via the registry)
-cp /usr/local/share/fonts/г/ГОСТ_тип_А.ttf fonts/
-
 docker build -t m1730-scale:latest .
 docker run -p 5000:5000 m1730-scale:latest
 ```
 
+Fonts are loaded from `fonts/` in the repo root; they are bundled into the image at build time.
+
 The production image is at `git.baumann.gr/adebaumann/m1730-generator`.
 
 ## Kubernetes