feat(firmware): read .typoena.snippets.json at boot into set_snippets

Mirror the prefs boot-read: load the git-tracked snippet library from the
SD repo, parse it with Snippets::parse, and hand it to the editor before
the first render. Missing/unreadable/malformed is non-fatal (no snippets,
editor runs). Verified serde_json builds for xtensa (cargo check, 0.6.0).

firmware/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "firmware"
-version = "0.5.0"
+version = "0.6.0"
 authors = ["Julien Calixte <juliencalixte@gmail.com>"]
 edition = "2024"
 resolver = "2"