Fix the Lint CI workflow (broken since v0.1.2)

clang-format job: the flatpak CI image has no ECM on the host, so the
configure step that generated .clang-format could never run. Commit the
ECM-generated .clang-format instead (it is MIT, LICENSES/MIT.txt added),
drop the container, pin clang-format 22.1.8 from PyPI to match the
version the tree is formatted with, and reformat the sources to match.

REUSE job: add the missing CC0-1.0 license text, a copyright line for
the metainfo, REUSE.toml coverage for README/CONTRIBUTING/.gitignore,
and REUSE-Ignore markers around CONTRIBUTING.md's SPDX example so the
parser stops reading prose as a license declaration. reuse lint now
passes locally (54/54 files).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019FXfh48mASRsE1WEhy9jcM

REUSE.toml

@@ -11,3 +11,12 @@ path = [
 ]
 SPDX-License-Identifier = "GPL-3.0-or-later"
 SPDX-FileCopyrightText = "ToServeTheKing <[email protected]>"
+
+[[annotations]]
+path = [
+    "README.md",
+    "CONTRIBUTING.md",
+    ".gitignore",
+]
+SPDX-License-Identifier = "CC0-1.0"
+SPDX-FileCopyrightText = "ToServeTheKing <[email protected]>"