multi-user: users, per-user profiles/filters/notifications, tab UI, apply forensics

* DB: users + user_profiles/filters/notifications/preferences; applications gets
  user_id + forensics_json + profile_snapshot_json; new errors table
  with 14d retention; schema versioning via MIGRATIONS list
* auth: password hashes in DB (argon2); env vars seed first admin; per-user
  sessions; CSRF bound to user id
* apply: personal info/WBS moved out of env into the request body; providers
  take an ApplyContext with Profile + submit_forms; full Playwright recorder
  (step log, console, page errors, network, screenshots, final HTML)
* web: five top-level tabs (Wohnungen/Bewerbungen/Logs/Fehler/Einstellungen);
  settings sub-tabs profil/filter/benachrichtigungen/account/benutzer;
  per-user matching, auto-apply and notifications (UI/Telegram/SMTP); red
  auto-apply switch on Wohnungen tab; forensics detail view for bewerbungen
  and fehler; retention background thread

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/templates/fehler_detail.html

@@ -0,0 +1,32 @@
+{% extends "_layout.html" %}
+{% block title %}Fehler #{{ error.id }} — lazyflat{% endblock %}
+{% block content %}
+<a href="/fehler" class="text-sm">← zurück zu den Fehlern</a>
+
+<section class="card p-5 space-y-2">
+    <div class="flex items-center gap-2 flex-wrap">
+        <h2 class="font-semibold text-lg">Fehler #{{ error.id }}</h2>
+        <span class="chip chip-bad">{{ error.kind }}</span>
+        <span class="chip chip-info">{{ error.source }}</span>
+    </div>
+    <div class="text-sm text-slate-600">
+        {{ error.timestamp }} · {{ error.summary or "(kein Text)" }}
+    </div>
+    {% if context %}
+    <details class="mt-2">
+        <summary class="font-medium">Kontext</summary>
+        <pre class="mono whitespace-pre-wrap break-all mt-2 p-3 bg-[#f6fafd] rounded-lg border border-soft">{{ context | tojson(indent=2) }}</pre>
+    </details>
+    {% endif %}
+</section>
+
+{% if application %}
+<section class="card p-5">
+    <h3 class="font-semibold mb-2">Zugehörige Bewerbung</h3>
+    <div class="text-sm">
+        <a href="/bewerbungen/{{ application.id }}">Bewerbung #{{ application.id }} öffnen</a>
+        — vollständige Forensik dort.
+    </div>
+</section>
+{% endif %}
+{% endblock %}