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>

launchd/de.surke.ssr.sync.plist

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
+  "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <key>Label</key>
+  <string>@@LABEL@@</string>
+
+  <key>ProgramArguments</key>
+  <array>
+    <string>@@SSR_BIN@@</string>
+    <string>sync</string>
+  </array>
+
+  <key>StartCalendarInterval</key>
+  <dict>
+    <key>Hour</key>
+    <integer>@@HOUR@@</integer>
+    <key>Minute</key>
+    <integer>@@MINUTE@@</integer>
+  </dict>
+
+  <key>RunAtLoad</key>
+  <false/>
+
+  <key>StandardOutPath</key>
+  <string>@@LOG_DIR@@/sync.out.log</string>
+
+  <key>StandardErrorPath</key>
+  <string>@@LOG_DIR@@/sync.err.log</string>
+
+  <key>EnvironmentVariables</key>
+  <dict>
+    <key>PATH</key>
+    <string>/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin</string>
+  </dict>
+
+  <key>ProcessType</key>
+  <string>Background</string>
+
+  <key>LowPriorityIO</key>
+  <true/>
+</dict>
+</plist>