Integrate macOS backup exclude lists into default config template

The init-generated config now ships with a comprehensive home snapshot
exclude list (caches, trash, cloud-synced data, rebuildable app state,
device backups) derived from a battle-tested rsync backup script, plus
an apps snapshot for /Applications excluding Apple-redownloadable apps
(Safari, GarageBand, iWork, iMovie) and large third-party installs.

Obsolete pre-Catalina app entries (Dashboard, iTunes, DVD Player, etc.)
were dropped — OS apps live in /System/Applications on modern macOS and
never appear in /Applications.

Adds a test asserting the template parses as valid YAML with the
expected snapshot structure.

internal/cli/init.go

@@ -22,13 +22,98 @@ age_recipients:
 
 # Named snapshots. Each snapshot backs up one or more paths and can have its
 # own exclude patterns in addition to the global excludes below.
+#
+# Exclude pattern semantics:
+#   - Patterns starting with / are anchored to the snapshot path root
+#     (e.g. "/Library/Caches" matches only ~/Library/Caches in a ~ snapshot)
+#   - Patterns without a leading / match anywhere in the tree
+#     (e.g. ".cache" matches any directory named .cache at any depth)
+#   - Globs are supported: *, **, ?
 snapshots:
   home:
     paths:
-      - ~/Documents
-      - ~/Pictures
-    # exclude:
-    #   - "*.cache"
+      - "~"
+    exclude:
+      # Trash, temp, and filesystem metadata
+      - "/.Trash"
+      - "/.Trashes"
+      - "/.fseventsd"
+      - "/.Spotlight-V100"
+      - "/.TemporaryItems"
+      - "/tmp"
+      - "/.rnd"
+      - ".DS_Store"
+      # Caches and package manager state (rebuildable)
+      - ".cache"
+      - ".bundle"
+      - "/.cpan/build"
+      - "/.cpan/sources"
+      - "/.gradle/caches"
+      - "/.docker"
+      - "/.dropbox"
+      - "/.minikube/cache"
+      - "/.local/share/containers/podman/machine"
+      - "/.persepolis"
+      - "/Library/Caches"
+      - "/Library/Logs"
+      - "/Library/Cookies"
+      - "/Library/Metadata"
+      - "/Library/Suggestions"
+      - "/Library/PubSub"
+      - "/Library/Homebrew"
+      - "/Library/Developer"
+      - "/Library/Parallels"
+      - "/Library/Google/GoogleSoftwareUpdate"
+      - "/Library/Preferences/Macromedia/Flash Player"
+      - "/Library/Preferences/SDMHelpData"
+      - "/Library/VoiceTrigger/SAT"
+      # Cloud-synced or restorable-from-server data
+      - "/Library/Mail"
+      - "/Library/Mail Downloads"
+      - "/Library/Safari"
+      - "/Library/Application Support/Evernote"
+      - "/Library/Application Support/MobileSync"
+      - "/Library/Application Support/SyncServices"
+      - "/Library/Application Support/protonmail/bridge/cache"
+      - "/Library/Application Support/Syncthing/index-*"
+      - "/Library/Syncthing/folders"
+      - "/Documents/Dropbox/.dropbox.cache"
+      # Large rebuildable app data (games, media caches, device backups)
+      - "/Applications/Fortnite"
+      - "/Documents/Steam Content"
+      - "/Library/Application Support/Ableton"
+      - "/Library/Application Support/CrossOver Games"
+      - "/Library/Application Support/SecondLife/cache"
+      - "/Library/Application Support/Steam/SteamApps"
+      - "/Library/Containers/com.docker.docker"
+      - "/Library/Group Containers/group.com.apple.secure-control-center-preferences"
+      - "/Library/iTunes/iPad Software Updates"
+      - "/Library/iTunes/iPhone Software Updates"
+      - "/Movies/CacheClip"
+      - "/Movies/ProxyMedia"
+      - "/Music/iTunes/Album Artwork"
+      - "/Pictures/iPod Photo Cache"
+
+  # Third-party applications. OS-provided apps live in /System/Applications
+  # on modern macOS and are never in /Applications, but Apple-installed
+  # App Store apps (Safari, GarageBand, iWork, iMovie) are excluded since
+  # they are re-downloadable.
+  apps:
+    paths:
+      - /Applications
+    exclude:
+      - ".DS_Store"
+      - "/Safari.app"
+      - "/GarageBand.app"
+      - "/iMovie.app"
+      - "/Keynote.app"
+      - "/Numbers.app"
+      - "/Pages.app"
+      - "/Xcode.app"
+      - "/Spotify.app"
+      - "/Steam.app"
+      - "/VirtualBox.app"
+      - "/Utilities/Adobe Installers"
 
 # Storage backend (pick ONE of the three forms below).
 #