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.

Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /app
 COPY web/requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt gunicorn
 
-COPY fonts/ГОСТ_тип_А.ttf /usr/local/share/fonts/г/ГОСТ_тип_А.ttf
+COPY fonts/ /app/fonts/
 
 COPY web/ .