chore: clean hydrotech-beam syncthing conflicts and add new docs

- Remove all .sync-conflict-* files
- Remove temp _temp_part_properties.json files
- Add USER_GUIDE.md
- Add dashboard docs (Executive, Technical, Operations, Master Plan)
- Add playbooks (DOE, NX_REAL_RUN, SYNCTHING_RECOVERY)
- Update iteration results

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

projects/hydrotech-beam/studies/01_doe_landscape/iterations/iter005/_temp_mass.txt

@@ -1 +1 @@
-p173=1205.9185440163983
+1205.918544016398

projects/hydrotech-beam/studies/01_doe_landscape/iterations/iter005/results.json

@@ -1,6 +1,6 @@
 {
   "iteration": 5,
-  "mass_kg": NaN,
+  "mass_kg": 1205.918544016398,
   "tip_displacement_mm": 17.29557228088379,
   "max_von_mises_mpa": 106.283703125,
   "feasible": false,