docs: generate config/properties.rst from fess_config.properties

[marevol]

Requires codelibs/fess#3434, which adds the group-heading marker this reads, and
codelibs/fess#3435, which drops four keys whose value had no effect — the pages here are
generated against both, so they show 635 keys rather than 639. Merge those first. Supersedes
#532 — that PR hand-fixed the jcifs names on this page; the generated page picks them up
from fess_config.properties automatically. Merge or close #532 either way; this
replaces the file wholesale.

What was wrong

config/properties.rst was maintained by hand. Measured against fess_config.properties:

• 120 keys missing — the whole api.* family, app.cipher.algorithm, and more.
• 10 keys that no longer exist, several under a misspelling: app.cipher.algorism,
  app.digest.algorism, domain.tile, http.proxy.Host, app.encrypt.key,
  cookie.default.expires, crawler.document.alphanum.term.size,
  online.help.name.esreq, query.gsa.index.field.content_type,
  app.encrypt.property.patterns. domain.tile had even acquired a description invented
  to match the typo: "The domain name of the tile server."

And it was English-only and orphaned: all seven config/index.rst hold the same 39
entries and this page is in none of them. Sphinx builds documents outside the toctree, so
it was published but unreachable from navigation —
fess.codelibs.org/15.8/config/properties.html returns 200 while the Japanese path
returns 404. It has been carried forward by create_version.sh since 14.17.

What this does

Generates the tables from fess_config.properties, so the page cannot drift from the
configuration it documents, and adds the page to all seven languages.

file	owns
fess_config.properties (fess repo)	keys, defaults, English descriptions, headings, order
<lang>/15.9/config/properties.po	translations, per language and per version
<lang>/15.9/config/properties.rst	generated between the GENERATED markers; the title and intro are outside them and stay editable

tools/gen_properties_doc.py follows tools/update_eol.py: same marker convention, same
--check mode, a sibling test file, standard library only. It carries a minimal .po
reader because Python's gettext reads compiled .mo, not .po — real gettext format,
so Poedit, Weblate and msgfmt --check all work on the catalogues.

tools/update_properties_doc.sh is run by hand against a fess checkout. Nothing is
vendored here.

What CI can and cannot check

fess_config.properties is not copied into this repository, so --check cannot
compare a page against fess. Divergence there surfaces when someone runs the script; the
generated block says so and names it.

What --check does verify, offline, is that the pages have not drifted from each other or
from their catalogues. Exercised against four kinds of tampering, each caught with exit 1:

tampering	what --check says
a description edited in place in ja	'…' is neither the English text nor a translation in ja/15.9/config/properties.po
a default value changed in ja	keys, defaults or table layout differ from en -- regenerate with tools/update_properties_doc.sh
a table row deleted from ja	same
the GENERATED-END marker removed	no GENERATED-BEGIN/END markers in the page

Translation

The catalogues ship with every msgstr empty, so all seven languages start in English and
gain their translation as a catalogue is filled. English gets no catalogue — it is what
fess_config.properties already holds.

Verified end to end by translating three entries into Japanese and regenerating: the
section heading, the table caption and the description all switched, --check stayed
green, and the CJK section underline came out at the right width because it is generated
from display columns rather than character count (docutils measures a title in columns, so
a character-counted underline is too short and the section is silently dropped). Reverted
before committing so the catalogues ship empty as designed.

Because the catalogues live inside the version tree, create_version.sh carries them into
a new version with its existing cp -r — no change to that script.

Verification

• python -m unittest discover -s tools — 79 tests, 0 failures (55 new, plus the existing
  update_eol suite unaffected).
• tools/gen_properties_doc.py --check — the 7 pages agree.
• tools/update_eol.py --check — unaffected.
• tools/check_headings.py on all seven 15.9 trees — clean.
• Every generated block parsed with docutils — 0 warnings in all seven languages,
  including the translated Japanese variant. Descriptions carrying Access-Control-* and
  api.cors.* are escaped, so they no longer risk tripping inline-markup recognition.
• Regenerating twice is a no-op (no change).
• The English page goes from 529 keys to 639: 120 added, 10 stale removed.

Size

25 files, roughly +28,000 lines: 7 pages of 639 rows each and 6 catalogues. The bulk is
generated and regenerable from one command.