docs: update msfs-data-import.md after clean-slate reset

- Cleared all MSFS-derived (address-geocoded) GPS
- Only real field GPS (28 assets from photo EXIF) remains
- Documented backup locations and clean-slate process

Refs #46

.gitignore

@@ -1,11 +1,12 @@
+cert.pem
 *.db
 *.db-journal
 *.db-shm
 *.db-wal
-uploads/*.jpg
-uploads/*.png
 key.pem
-cert.pem
+*.pre-msfs-import
 __pycache__/
-.venv/
+uploads/*.jpg
 uploads/photos/
+uploads/*.png
+.venv/