…es; template-based system.properties; fetch theme from fess-themes

…lasticsearch, ignore scratch/bulk and legacy theme assets)

…verlay

Generate data/fess/opt/fess/fess_config.properties from the upstream base
(pinned by FESS_VERSION in .env) plus conf/fess_config.overlay.properties,
instead of -Dfess.config.* flags. Restores the source-code aware
index.filetype map (a multi-line value that cannot be passed as a -D flag)
and keeps only the codesearch delta in git; the base auto-tracks the pinned
Fess version on upgrade. Secrets stay out of git via the optional,
git-ignored conf/fess_config.local.properties.

- .env: single source of truth for FESS_VERSION / OPENSEARCH_VERSION,
  used by compose.yaml image tags and the config base fetch
- bin/render-fess-config.sh: fetch base (cached per version), strip
  overridden keys (handling backslash continuations), append overlay/local
- bin/setup.sh: run the renderer after generating system.properties
- compose.yaml: drop the -Dfess.config.* block; use ${FESS_VERSION} / ${OPENSEARCH_VERSION}
- README: document the overlay workflow, secrets, and version upgrades

…0); bump fess-ds-git to 15.7.0

setup.sh clones the branch named by FESS_THEMES_BRANCH (default: main) so the
codesearch theme can be fetched from the unmerged fess-themes PR #23
(branch feat/codesearch-theme) for testing. Document the override in README.

…r theme merge

- .env: OPENSEARCH_VERSION 3.6.0 -> 3.7.0
- compose.yaml: remove internal TODO comment (theme mount path is verified)
- README: drop the obsolete fess-themes PR-branch note (theme merged to main);
  replace the first-run note; fix the access-token guide link to 15.7; note the
  ACCESS_TOKEN/jq requirements for register_github.sh; clarify the Data Crawler
  step; add a re-index note under Updating
- setup.sh: make FESS_THEMES_BRANCH comments generic now that the theme is merged

Replace the custom curl helper with the official Fess admin-API CLI (codelibs/fessctl).

- README: install/configure fessctl (pipx/uv), register a repo via
  'fessctl dataconfig create' (GitDataStore with the codesearch handler-script
  that fills organization/repository/filetype facets), and crawl via
  'fessctl scheduler start default_crawler' (crawls all data configs, no restart).
- Remove bin/register_github.sh (superseded by fessctl).
- Add fessctl to the Architecture overview; update the re-index note to use it.

…repo

One-command convenience wrapper around fessctl:
- auto-detects the repository's default branch (git ls-remote)
- builds the codesearch GitDataStore config (handler-script fills the
  organization/repository/filetype facets) and creates it via 'fessctl dataconfig create'
- starts the Default Crawler ('fessctl scheduler start default_crawler')
- flags + env + defaults (FESS_ENDPOINT/FESS_ACCESS_TOKEN/FESS_VERSION), --help,
  --no-crawl, --domain/--branch/--owner/--homepage
- idempotent (skips create if the data store already exists); validates deps
  (fessctl, git, python3) and inputs

The README fessctl steps remain the primary reference; this script just bundles them.