feat: implement administrator-driven audit log purging with forced archival download

- Created find_older_than and delete_older_than database repository methods.
- Built a /auth/audit/purge POST endpoint that validates retention days (min 1 day).
- Serializes and streams matching logs as an attachment JSON download for archival before database deletion.
- Added a 'Purge Logs' button and modal interface in the administrator dashboard, automatically reloading the view after download.

templates/auth/password.html

@@ -79,23 +79,6 @@
                             </div>
                         </div>
                     </div>
-
-                    <div class="p-5 rounded-2xl bg-indigo-500/5 border border-indigo-500/10 flex items-start gap-4">
-                        <div class="w-10 h-10 rounded-xl bg-indigo-500/10 flex items-center justify-center text-indigo-400 flex-shrink-0">
-                            <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor" class="w-5 h-5">
-                                <path stroke-linecap="round" stroke-linejoin="round" d="M15 19.128a9.38 9.38 0 0 0 2.625.372 9.337 9.337 0 0 0 4.121-.952 4.125 4.125 0 0 0-7.533-2.493M15 19.128v-.003c0-1.113-.285-2.16-.786-3.07M15 19.128v.109A12.318 12.318 0 0 1 8.624 21c-2.331 0-4.512-.645-6.374-1.766l-.001-.109a6.375 6.375 0 0 1 11.964-3.07M12 6.375a3.375 3.375 0 1 1-6.75 0 3.375 3.375 0 0 1 6.75 0Zm8.25 2.25a2.625 2.625 0 1 1-5.25 0 2.625 2.625 0 0 1 5.25 0Z" />
-                            </svg>
-                        </div>
-                        <div>
-                            <h4 class="text-sm font-bold text-slate-200">Developer Roster</h4>
-                            <p class="text-xs text-slate-400 mt-1 leading-relaxed">Manage team developer profiles, update their technical skills, or clear their metadata.</p>
-                            <div class="mt-4">
-                                <a href="/developers" class="inline-flex items-center justify-center rounded-xl text-xs font-bold transition-all px-4 py-2.5 bg-secondary border border-border hover:bg-secondary/80 text-slate-200">
-                                    Manage Developers
-                                </a>
-                            </div>
-                        </div>
-                    </div>
                 </div>
             </div>