P2 cleanups: pin deps, prune job-run rows, unmask non-secret creds, enforce allowlist at login

- R11: pin requirements.txt to the versions running in the image, so a rebuild
  can't pull a breaking upstream release. Documented how to upgrade.
- R12: log rotation now also prunes job_runs rows older than 90 days (nulling
  the manual_imports FK reference first), so the table doesn't grow without
  bound. dedup/genre candidates are review state and left alone.
- U5: credential form shows non-secret fields (URLs, usernames, prefs) as plain
  text so they can be verified while typing; only real secrets stay masked.
  Dashboard IP card reworded from gluetun-specific to generic "Outbound IP".
- S9: enforce ALLOWED_EMAIL at the OIDC callback, before any user row or session
  is created, instead of only on later requests.

Verified: pinned build resolves; prune deletes only old rows and keeps the
manual_imports record; credentials page renders text+password inputs; a
disallowed email gets 403 with no user row, an allowed one succeeds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/services/scheduler_service.py

@@ -85,7 +85,10 @@ async def _genre_run(triggered_by: str = "schedule"):
 
 
 async def _log_rotation(triggered_by: str = "schedule"):
-    """Replaces `find /var/log/sldl -name '*.log' -mtime +30 -delete`."""
+    """Replaces `find /var/log/sldl -name '*.log' -mtime +30 -delete`, and also
+    prunes old job_runs rows so the database doesn't grow without bound."""
+    from app.db import prune_old_job_runs
+
     cutoff = time.time() - 30 * 86400
     removed = 0
     if settings.logs_dir.exists():
@@ -93,7 +96,8 @@ async def _log_rotation(triggered_by: str = "schedule"):
             if path.is_file() and path.stat().st_mtime < cutoff:
                 path.unlink(missing_ok=True)
                 removed += 1
-    return removed
+    pruned_rows = prune_old_job_runs()
+    return {"logs_removed": removed, "job_run_rows_pruned": pruned_rows}
 
 
 MAINTENANCE_JOBS: dict[str, tuple[dict, callable]] = {