Fix audit findings: path traversal, exec shell, glob dup, dead bread-sync, version drift

- modules_mgmt.rs: reject module names containing path separators, `..`,
  or absolute paths before joining onto modules_dir (install_from_local,
  remove_module, read_module_manifest); adds canonicalized containment
  check as defense in depth. Manifest-supplied names and CLI args were
  previously joined unsanitized, allowing path traversal on install/remove.
- breadd/src/lua/mod.rs: bread.exec now runs via `sh -c` instead of
  `sh -lc`; no documented reason was found for login-shell semantics.
- Unify the two independently hand-written glob matchers (subscription
  dispatch in breadd/src/core/subscriptions.rs vs. the CLI --filter path
  in breadd/src/ipc/mod.rs) into one implementation in
  bread-shared/src/glob.rs, used by both call sites.
- Remove the dead bread-sync/ tree (already excluded from the workspace
  and fully unreferenced) and its stale PKGBUILD deps (libgit2, git
  optdepend) and packaging docs mention.
- Correct the version-number transposition bug ("6.2.0" instead of
  "0.6.2"/"0.6.6") across bread-shared, breadd, and bread-cli Cargo.toml,
  and fix PKGBUILD's stale pkgver, so Cargo.toml/doctor/PKGBUILD all agree
  with the latest git tag (v0.6.6).

breadd/src/lua/mod.rs

@@ -540,7 +540,7 @@ impl LuaEngine {
         let exec_fn = self.lua.create_function(move |_lua, cmd: String| {
             task::spawn_blocking(move || {
                 match std::process::Command::new("sh")
-                    .arg("-lc")
+                    .arg("-c")
                     .arg(&cmd)
                     .status()
                 {