Fix wrapped-course false positive in picker; add build version display

Sort Unsorted's destination picker still listed a course whose real
video content sat two levels deep inside its own "display name"
folder (a common release-bundle extraction shape), alongside empty
leftover folders from the extraction that neither of the two earlier
exclusion checks could safely rule out - an empty folder is
indistinguishable from a legitimate freshly-created category. Detect
this case by comparing token similarity between a folder's own name
and its single course child's name: high overlap means they're naming
the same thing (a redundant wrapper), not a deliberate category
holding one course.

Also bake the build's git commit + build time into the Docker image
(git rev-parse at build time, .git deleted again immediately after) so
a push's effect on the running container is actually visible - shown
on the Settings page and in /health - instead of having to guess
whether a webhook rebuild picked up the latest commit.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

templates/settings.html

@@ -466,6 +466,10 @@
             <button class="btn btn-secondary" onclick="resetSettings()">Reset to Defaults</button>
             <span id="save-status">{{ icons.icon('check', 14) }} Saved</span>
         </div>
+
+        <p style="text-align: center; color: var(--text-muted); font-size: 0.8em; margin-top: 30px;">
+            Version {{ build_version }}
+        </p>
     </div>
     </div>