feat(profile): add password change and activity filters

Implement password change API and UI in the Account tab
Add secondary filters for contributions, reactions, and comments
Display referral summary in the profile header

frontend/src/styles/main.css

@@ -4376,6 +4376,10 @@ button:disabled,
   grid-column: 2;
 }
 
+.profile-card--password {
+  grid-column: 1 / -1;
+}
+
 .profile-identity {
   display: grid;
   grid-template-columns: auto minmax(0, 1fr);
@@ -4503,6 +4507,10 @@ button:disabled,
   min-width: 0;
 }
 
+.profile-secondary-tabs .tab-list {
+  border-bottom-color: color-mix(in srgb, var(--line) 72%, transparent);
+}
+
 .profile-layout--loading {
   grid-template-columns: minmax(260px, 0.5fr) minmax(0, 1fr);
 }
@@ -4566,6 +4574,50 @@ button:disabled,
   font-variant-numeric: tabular-nums;
 }
 
+.profile-referral-summary {
+  grid-column: 1 / -1;
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) auto;
+  gap: 10px;
+  align-items: center;
+  min-width: 0;
+  padding: 12px;
+  border: 1px solid var(--line);
+  border-radius: var(--radius-card);
+  background: var(--surface-soft);
+}
+
+.profile-referral-summary > div {
+  display: grid;
+  gap: 4px;
+  min-width: 0;
+}
+
+.profile-referral-summary span {
+  color: var(--muted);
+  font-size: 13px;
+  font-weight: 850;
+}
+
+.profile-referral-summary strong {
+  color: var(--ink-soft);
+  font-family: var(--font-mono);
+  font-size: 18px;
+  font-weight: 900;
+  overflow-wrap: anywhere;
+}
+
+.profile-referral-summary .ui-button {
+  min-height: 44px;
+  white-space: nowrap;
+}
+
+.profile-referral-summary .status-message {
+  position: static;
+  grid-column: 1 / -1;
+  box-shadow: none;
+}
+
 .profile-section-grid,
 .profile-account-grid {
   display: grid;
@@ -5188,7 +5240,8 @@ button:disabled,
     grid-template-columns: 1fr;
   }
 
-  .profile-card--referral {
+  .profile-card--referral,
+  .profile-card--password {
     grid-column: auto;
   }
 
@@ -5330,6 +5383,11 @@ button:disabled,
     grid-template-columns: 1fr;
   }
 
+  .profile-referral-summary {
+    grid-template-columns: 1fr;
+  }
+
+  .profile-referral-summary .ui-button,
   .profile-referral-link-row .ui-button {
     width: 100%;
   }