test: add unit tests for least-covered modules

[devin-ai-integration]

Summary

Measured per-file line coverage with cargo llvm-cov on cloudreve-api and cloudreve-sync, then added focused unit tests for the pure-logic modules that were least covered. No production code changed (only a one-line indentation fix in drive/utils.rs).

Coverage before → after (lines):

module	before	after
cloudreve-api/src/boolset/mod.rs	0%	100%
cloudreve-api/src/models/uri.rs	13%	98%
cloudreve-api/src/error.rs	36%	91%
cloudreve-sync/src/uploader/encrypt.rs	0%	100%
cloudreve-sync/src/drive/utils.rs	50%	99%

Workspace line coverage (api + sync) rose ~28% → ~38%. +58 new tests, all inline #[cfg(test)] mod tests blocks matching the repo's existing style.

What the tests exercise:

• boolset: bit get/set with storage expansion, and/or across differing lengths, base64 round-trip + decode-error fallbacks in from_data.
• uri (CrUri): prefix validation, component parsing, percent-encoding round-trips (set_path/join/join_raw), parent, SearchParam set↔parse round-trips including the trash restore_uri metadata path and pure_uri filtering.
• error: ErrorCode::from_code mapping, is_credential_error, and every ApiError::from_response branch (lock conflict, batch w/ aggregated errors, auth→LoginRequired, generic fallback) plus is_token_expired/requires_login.
• encrypt (EncryptionConfig): metadata validation (bad base64 / wrong key & IV lengths), CTR reversibility, and that chunked encrypt_at_offset (both block-aligned and non-aligned offsets) matches a single full-buffer pass — the property the resumable uploader relies on.
• drive/utils: local_path_to_cr_uri / remote_path_to_local_relative_path round-trips incl. out-of-root errors, and view_online_url / recycle_bin_url query construction.

Test plan

cargo test -p cloudreve-api -p cloudreve-sync passes (mirrors CI). New tests are deterministic and require no network/DB.

Link to Devin session: https://app.devin.ai/sessions/47a90a862b514e589db48d6ff39765fc
Requested by: @cedev-1

[devin-ai-integration]

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