Fix clippy warnings and add Gitea CI pipeline

Clippy fixes:
- clawhdf5-onion/reader.rs: introduce RawPage type alias to resolve
  type_complexity lint on revision_pages_raw return type
- clawsync-onion/iblt.rs: remove stray #[forbid(unsafe_code)] module
  attribute (crate-level forbid already in lib.rs; the module attr was
  useless and triggered the empty-line-after-attribute lint)
- clawsync-onion/differ.rs: replace ok_or_else(|| …) with ok_or(…)
  for non-lazily-constructed error values
- clawsync-cli/main.rs: accept &Path instead of &PathBuf in
  handle_hdf5_client to avoid unnecessary indirection

CI (.gitea/workflows/ci.yml):
- test job: cargo test --workspace (default + simd-cdc)
- lint job: cargo clippy -D warnings + cargo fmt --check
- msrv job: build + test on Rust 1.85 (workspace rust-version)
- publish-dry-run job: cargo publish --dry-run for clawsync-core

All 573 tests still passing after fixes.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

crates/clawhdf5-onion/src/reader.rs

@@ -9,6 +9,9 @@ use crate::error::OnionError;
 use crate::format::Codec;
 use crate::writer::OnionFile;
 
+/// `(h5_offset, compressed_data, codec_byte, orig_size)` — raw page as stored.
+pub type RawPage = (u64, Vec<u8>, u8, u32);
+
 /// Selector for which revision to open.
 #[derive(Debug, Clone)]
 pub enum OpenRevision {
@@ -201,7 +204,7 @@ impl OnionFile {
     pub fn revision_pages_raw(
         &self,
         rev: u64,
-    ) -> Result<Vec<(u64, Vec<u8>, u8, u32)>, OnionError> {
+    ) -> Result<Vec<RawPage>, OnionError> {
         let table = self
             .page_tables
             .get(rev as usize)