Adds services/silent-send.sh — installs the Silent Send browser extension
(client-side PII redaction for AI chat). Non-docker module: installs git +
Node.js >=18 (NodeSource) + npm, clones outis1one/silent-send to ~/silent-send,
runs npm install (readies web-ext for Firefox build/sign), optionally builds a
signed Firefox .xpi, and prints per-browser load/build instructions. README
written to the checkout.
Introduces a new 'extras' category for non-docker add-ons pulled from other
repos, wired into setup.sh CATEGORY_ORDER (gaming -> extras -> backup) with an
is_installed marker. MODULAR.md groups list updated.
Bumps version to 0.9.9.
