feat(app): implement Product Scan review flow, dynamic batch expiry picker, custom PDFs, PO relationships, and aligned card layouts

AGENTS.md

@@ -104,11 +104,18 @@ no clear "done" condition). If so:
 - Skip this step entirely when the task is already unambiguous — don't grill the
   user on obvious work.
 
+### 2b. TDD Workflow (Test First)
+
+- **Write Tests First**: Before implementing the actual feature code for a task, write automated tests defining the expected behavior.
+- **Iterate Until Green**: Run the tests to confirm they fail, then write the implementation until all tests pass perfectly.
+- **Browser Testing**: If the enhancement involves web UI or visual components, use browser tools (e.g., Chrome) to test the app visually and functionally if necessary.
+
 - Implement the selected task(s) fully in the codebase, applying the relevant role(s)
   from `SKILLS.md` (Architect, Backend, Frontend, QA, Hardware/Compatibility).
 - Once complete:
   1. Update the task's status in `/plans/next-enhancements.md` to `[DONE]`.
   2. Document the new/updated feature in `/docs/feature-list.md` under the right section heading.
+  3. **Create an Iteration Log**: Perform a code review and audit of the tasks just completed. Document this audit in `/docs/iteration-log.md` (or append to it) to ensure all functions work perfectly.
 - **Verify build integrity** — this is not just "it compiles and runs":
   - QA pass: exercise the golden path and edge cases; run/extend automated tests.
   - Hardware/Compatibility pass: check cross-platform, cross-browser, and resource