release/: the newest stage's manufacturing files and documentation

A stage tag (v*) now builds, with kicad-cli, pandoc and pdflatex in the CI
image (.gitea/scripts/release-files.py):
- per board: Gerbers + Excellon drill zip (JLCPCB-compatible settings), BOM
  (grouped, DNP left out), pick and place, schematic and PCB PDFs, 3D renders;
- docs/*.md and docs/tex/*.tex as PDF, tag and commit in the footer;
- release/README.md with tag, commit, ERC/DRC result, files, SHA-256 and the
  stage's CHANGELOG section.
Every file name carries the tag. release-attach.py attaches the files plus a
zip of the whole folder to the tag's release (replacing assets of an earlier
run); for the newest stage tag (not older stages, not pre-releases) the job
commits them to release/ on main with [skip ci].

.gitignore: !/release/ after Release/ (Windows matches it case-insensitively);
.gitattributes: release/** -text so the SHA-256 match on every checkout.
TEMPLATE.md: "Release files" section, rules and CI updated.

Tested in git.b4l.co.th/b4l/kicad10_auto_node with harNES's board and docs:
v0.1 committed, v0.0 and v0.2-rc.1 left release/ alone, v0.2 tagged on an
older commit landed on top of a moved main; uploads byte-exact against a stub
of the Gitea release API.

docs/README.md

@@ -3,3 +3,7 @@
 Datasheets of the parts in `docs/datasheets/`, LaTeX sources in `docs/tex/`.
 A `docs/input.md` (typecad-docgen front matter) turns on the fabrication
 document workflow.
+
+At every stage tag CI prints each `docs/*.md` (except this README and
+`input.md`) and each LaTeX document in `docs/tex/` as PDF into `release/docs/`,
+with the tag in the file name and the footer.

docs/tex/README.md

@@ -1,3 +1,6 @@
 # LaTeX sources
 
-Sources of the developer documentation.
+Sources of the developer documentation. Every `.tex` file here with a
+`\documentclass` is built with pdflatex (and bibtex when it cites) into
+`release/docs/` at a stage tag; included parts without one are not built on
+their own.