Initial ssr repository

Convert the legacy system_sync.sh and system_restore.sh into a modular
shareable repository:

- bin/ssr CLI dispatcher with install/sync/restore/schedule/config/status
- lib/ split: common, cloud, brew, mackup, macos
- Cloud provider abstraction (icloud, dropbox, googledrive, onedrive, custom)
- launchd template for scheduled daily sync (renderable via sed)
- ssr.conf.example with whitelisted KEY=VALUE config loader
- macos-defaults.sh extracted from inline block, overridable
- install.sh bootstrap symlinks CLI into ~/.local/bin
- README with usage, config table, migration map, security notes
- Original scripts archived under legacy/ for reference

Fixes vs originals: set -euo pipefail, quoted vars, find -print0,
spctl --global-disable (was --master-disable), MACOS=".macos" bug,
zero-width char before ln, Apple Silicon brew shellenv, config injection
hardening.

Co-authored-by: Cursor <cursoragent@cursor.com>

legacy/system_sync.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+LOGGER_BIN="/usr/bin/logger -ist '$0'"
+UUID=$(system_profiler SPHardwareDataType | awk '/UUID/ { print $3; }')
+HOSTNAME=$(hostname -s)
+BACKUPDIR="$HOME/Library/Mobile Documents/com~apple~CloudDocs/BACKUP/$HOSTNAME - $UUID"
+
+# Check for Homebrew to be present, install if it's missing
+if test ! $(which brew); then
+    echo "Installing homebrew..."
+    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
+fi
+BREW_BIN=$(which brew)
+BREW_PREFX=$(brew --prefix)
+CASK_DIR=$(brew --caskroom)
+
+# Update homebrew recipes
+$BREW_BIN update
+MACKUP_DIR="$HOME/Library/Mobile Documents/com~apple~CloudDocs/Mackup"
+MACKUP_BIN=$(which mackup)
+$MACKUP_BIN -f backup
+
+mkdir -vp "$BACKUPDIR"
+pushd "$BACKUPDIR" >/dev/null
+cp -vf Brewfile{,.bak}
+$BREW_BIN bundle dump --describe --quiet --force | $LOGGER_BIN
+popd >/dev/null