feat: add reactions, bookmarks, polls modules with session remember config

Add three new feature modules (reactions, bookmarks, polls) with corresponding database tables, indexes, and router registrations. Introduce `SESSION_MAX_AGE_REMEMBER` config for extended session duration, add `get_unread_messages` template global, and include operational defaults for rate limiting and session settings in `site_settings`.

devplacepy/static/css/messages.css

@@ -1,6 +1,6 @@
 .messages-layout {
     display: grid;
-    grid-template-columns: 320px 1fr;
+    grid-template-columns: minmax(0, 320px) 1fr;
     gap: 0;
     height: calc(100vh - var(--nav-height) - 2rem);
     background: var(--bg-card);
@@ -13,6 +13,7 @@
     border-right: 1px solid var(--border);
     display: flex;
     flex-direction: column;
+    min-width: 0;
 }
 
 .messages-list-header {
@@ -47,7 +48,6 @@
     padding: 0.625rem 1rem;
     font-size: 0.875rem;
     color: var(--text-primary);
-    transition: background 0.15s;
     text-decoration: none;
 }
 
@@ -65,7 +65,6 @@
     align-items: center;
     gap: 0.75rem;
     padding: 0.75rem 1rem;
-    transition: background 0.2s;
     cursor: pointer;
 }
 
@@ -207,7 +206,6 @@
     align-items: center;
     justify-content: center;
     font-size: 1rem;
-    transition: background 0.15s;
 }
 
 .messages-send-btn:hover {