(ui) Remove legacy-facing labels from operator pages

Replace refactor-era wording such as Source, Source root, SQL records,
database, runtime, and Django generation labels with operator-facing copy
around backup source, tracking records, changelog files, active config, and
pobsync-managed SSH keys.

Add view assertions so the old source/SQL labels do not quietly return.

Refs #24

src/pobsync_backend/self_check.py

@@ -266,13 +266,13 @@ def _config_checks() -> list[SelfCheck]:
     message = "Default global config exists."
     if global_config.backup_root != settings.POBSYNC_BACKUP_ROOT:
         status = "warning"
-        message = "Global config backup root differs from the runtime backup root."
+        message = "Saved backup root differs from the active backup root."
     return [
         SelfCheck(
             "Global config",
             status,
             message,
-            f"database={global_config.backup_root} runtime={settings.POBSYNC_BACKUP_ROOT}",
+            f"saved={global_config.backup_root} active={settings.POBSYNC_BACKUP_ROOT}",
         )
     ]