fix: resolve remaining CI check failures

- cargo deny: add MPL-2.0 and BSD-3-Clause to allow list (colored via
  simple_logger/mockito; encoding_rs via reqwest)
- conventional commits: use explicit SHA of last pre-conventional commit
  instead of from_latest_tag (no tags exist yet in the repo)
- MSRV: raise rust-version 1.80 -> 1.88 to match the actual minimum
  required by the dependency tree (simple_logger -> time 0.3 -> 1.88)
- MSRV CI: update toolchain pin to 1.88 to match
- macOS test: remove Swatinem/rust-cache from test matrix job to avoid
  stale cache corrupting the cargo binary path on arm64 runners

deny.toml

@@ -17,6 +17,8 @@ allow = [
     "MIT",
     "Apache-2.0",
     "Unicode-3.0",
+    "MPL-2.0",
+    "BSD-3-Clause",
 ]
 
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