## Implementation Plan: Fix Zip Service 100% Failure Rate

### Changes Required

1. **Apply the three blob‑resilience fixes to `master`** (if not already present).  
   The complete fix is on branch `typosaurus/ticket-68`.  
   - Either merge that branch into `master` or cherry‑pick the commits/apply the diffs.  
   - In `project_files.py` (locate via `grep -r "def export_to_dir"`) ensure:
     - **`export_to_dir`** – wrap each `shutil.copyfile(src, dst)` in `try/except (FileNotFoundError, OSError)`, log a warning, and `continue` (around current master line 710).
     - **`_export_node`** – same wrapper around `shutil.copyfile` (around master line 580).
     - **`delete_node`** – after the soft‑delete loop, iterate over binary nodes and call `_unlink_blob(row)` (around master line 466).
     - **`export_to_dir`** – confirm no call to `_guard_writable(project_uid)` remains (around master line 687).  
     *Exact line numbers may shift if intervening commits exist; verify by inspecting the diff.*

2. **Add missing test coverage for the blob‑missing scenario.**  
   In `tests/unit/services/jobs/zip_service.py`:
   - Create a test method, e.g. `test_zip_job_with_missing_blob_succeeds`.
   - Set up a project containing a binary file whose DB row exists but blob file is deleted from disk.
   - Enqueue a zip job and assert it completes with `status == "done"` and `bytes_out > 0`.
   - Confirm the resulting archive does not contain the missing file (log warning is sufficient; the test should not raise).

3. **Run verification commands.**  
   In a Python ≥3.12 environment:
   ```bash
   python3 -m venv .venv && source .venv/bin/activate
   pip install -e '.[dev]' -q
   make test-unit
   pip install -q ruff && ruff check .
   ```

### Definition of Done

- [ ] `git diff master..HEAD -- devplacepy/routers/projects/project_files.py` (or the correct path) shows exactly the three changes described above – no extra modifications.
- [ ] New test `test_zip_job_with_missing_blob_succeeds` exists in `tests/unit/services/jobs/zip_service.py` and can be identified by grep.
- [ ] Virtual environment created, dependencies installed without errors.
- [ ] `make test-unit` exits with exit code 0; the new test passes alongside all existing tests.
- [ ] `ruff check .` exits with exit code 0 (no lint errors on any file).
- [ ] Working tree is clean (no merge conflicts, no uncommitted changes unrelated to the fix).