fix: merge main into feature branch - resolve all 18 conflicts cleanly

Merges origin/main (v0.155.0) into the classification feature branch,
resolving all 18 conflicted files by accepting main's version and
re-applying only classification-specific additions:

- Renumber migration from 037 to 038 (chains from 037_user_sessions)
- Re-add ClassificationRuleModel to models.py, env.py, conftest.py
- Re-add classification_rules_router to api/__init__.py
- All session management, QR auth, and devices code preserved from main

Migration chain validated. 62 classification tests pass.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/templates/base.html

@@ -570,6 +570,7 @@
         profileSettings: {{ _("nav.profile_settings") | tojson }},
         mySubscription: {{ _("nav.my_subscription") | tojson }},
         apiTokens: {{ _("nav.api_tokens") | tojson }},
+        devices: {{ _("nav.devices") | tojson }},
         sharedLinks: {{ _("nav.shared_links") | tojson }},
         signOut: {{ _("nav.sign_out") | tojson }},
         logIn: {{ _("nav.login") | tojson }},