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/templates/credentials/index.html

@@ -54,8 +54,10 @@
           </label>
           {% if field in ("cookies_txt",) %}
           <textarea id="{{ scope }}_{{ field }}" name="{{ field }}" rows="6" placeholder="leave blank to keep current"></textarea>
-          {% else %}
+          {% elif field in secret_keys %}
           <input type="password" id="{{ scope }}_{{ field }}" name="{{ field }}" placeholder="leave blank to keep current" autocomplete="off">
+          {% else %}
+          <input type="text" id="{{ scope }}_{{ field }}" name="{{ field }}" placeholder="leave blank to keep current" autocomplete="off" spellcheck="false">
           {% endif %}
         </div>
         {% endfor %}