fix(lambdas): declare flowio dependency for FCS preview

preview.py was migrated from fcsparser to flowio for FCS parsing, but the
`preview` optional-dependency in lambdas/shared/pyproject.toml still pinned
`fcsparser~=0.2.1`. CI installs deps from the lockfiles, so `import flowio`
raised ModuleNotFoundError and every FCS code path fell through to the
"Unable to parse data or metadata" fallback — failing test_fcs in the
shared, indexer, and preview lambda suites.

Swap the extra to `flowio~=1.4` and regenerate every affected lockfile:
- workspace root uv.lock (shared + indexer resolve flowio transitively)
- standalone preview lock (depends on t4-lambda-shared[preview])
- standalone access_counts/pkgevents/tabular_preview/thumbnail/transcode
  locks, which embed t4-lambda-shared's requires-dist (including its preview
  extra) and otherwise fail `uv export --locked`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Austin Hovland

lambdas/access_counts/uv.lock

@@ -11,7 +11,7 @@ mem = [
     "psutil>=6",
 ]
 preview = [
-    "fcsparser~=0.2.1",
+    "flowio~=1.4",
     "numpy>=1.26,<3",
     "openpyxl>=3.1",
     "pandas>=2.2",