refactor(tests): migrate remaining batches to tests/common/

Finishes the lift of shared helpers into `tests/common/`. Covered:
- health, web, oneliners_api, upload (31 tests; upload exercises the
  new `multipart_upload_body` helper driven by doctate_common field
  constants)
- sse_integration, sse_cleanup, transcribe, oneliner_heal_decoupled,
  silent_case_empty, failed_only_case_empty_oneliner,
  transient_failure_retries (24 tests)

Also applied cargo fmt across the test tree and fixed one clippy
needless_borrows_for_generic_args warning in analyze_test.

All 387 tests pass; 3 ignored (as before).

Side effect: health_test previously used a hardcoded `/tmp/doctate-test`
data path, which parallel `cargo test` runs could collide on. The
migration replaces it with the common unique-tmpdir pattern, removing
a latent flake.

server/tests/common/config.rs

@@ -129,9 +129,7 @@ impl TestConfig {
     /// `Config::test_default` themselves are broken (not reachable in
     /// practice).
     pub fn build(self) -> Arc<Config> {
-        let data_path = self
-            .data_path
-            .unwrap_or_else(|| unique_tmpdir(self.label));
+        let data_path = self.data_path.unwrap_or_else(|| unique_tmpdir(self.label));
         let api_keys: HashMap<String, String> = self
             .users
             .iter()