Email filter: custom dropdown with SVG icons for each option

The All/Unread/Favorites/etc selector was a native <select>, which
can't render SVG inside <option>. Replace it with a custom picker
that:

- Keeps the existing <select id="email-lib-filter"> as the value
  store (hidden via display:none). All existing 'change' listeners
  keep working — the picker just dispatches a change event after
  updating the select's value.
- Renders a styled button + drop-out menu built from the select's
  options (preserves optgroup labels like 'Tags').
- Each option carries an SVG icon: lines for All, ringed dot for
  Unread, star for Favorites, empty checkbox for Undone, bell for
  Reminders, reply arrow for Unanswered/Reply-soon, clock for
  Pending, calendar-x for Stale, exclamation-triangle for Urgent,
  ban for Spam, newsletter and megaphone for the marketing tags.
- Icons use var(--accent) so they pick up the user's theme color.
- Click outside / Esc closes the menu (Esc handler is capture-phase
  + stopPropagation so it doesn't bubble to the modal-close listener
  and shut the whole email window).

CSS scoped under .email-filter-picker.

static/style.css

@@ -11046,6 +11046,130 @@ textarea.memory-add-input {
   border-color: var(--red);
 }
 
+/* Custom email filter picker (All / Unread / Favorites / …). Replaces the
+   native <select> so options can carry SVG icons. The hidden source
+   <select id="email-lib-filter"> is the value store and dispatches
+   'change' on selection. */
+.email-filter-picker {
+  position: relative;
+  top: 3px;
+}
+.email-filter-btn {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  width: 100%;
+  background: var(--bg);
+  color: var(--fg);
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  font-family: inherit;
+  font-size: 11px;
+  height: 24px;
+  padding: 0 8px 0 8px;
+  cursor: pointer;
+  text-align: left;
+  transition: border-color 0.12s, background 0.12s;
+}
+.email-filter-btn:hover { border-color: color-mix(in srgb, var(--accent, var(--red)) 50%, var(--border)); }
+.email-filter-btn:focus-visible {
+  outline: none;
+  border-color: var(--accent, var(--red));
+}
+.email-filter-current {
+  flex: 1;
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.email-filter-icon {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 13px;
+  height: 13px;
+  color: var(--accent, var(--red));
+  flex-shrink: 0;
+}
+.email-filter-icon svg { width: 13px; height: 13px; }
+.email-filter-label {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+.email-filter-caret {
+  flex-shrink: 0;
+  opacity: 0.6;
+  transition: transform 0.15s;
+}
+.email-filter-picker .email-filter-btn[aria-expanded="true"] .email-filter-caret {
+  transform: rotate(180deg);
+}
+
+.email-filter-menu {
+  position: absolute;
+  top: calc(100% + 4px);
+  left: 0;
+  right: 0;
+  z-index: 100;
+  max-height: 320px;
+  overflow-y: auto;
+  background: var(--panel, var(--bg));
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  box-shadow: 0 6px 20px rgba(0,0,0,0.22);
+  padding: 4px;
+  display: flex;
+  flex-direction: column;
+  gap: 1px;
+}
+.email-filter-menu[hidden] { display: none; }
+.email-filter-group {
+  font-size: 9px;
+  font-weight: 600;
+  letter-spacing: 0.6px;
+  text-transform: uppercase;
+  opacity: 0.55;
+  padding: 8px 9px 3px;
+}
+.email-filter-item {
+  all: unset;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  width: 100%;
+  padding: 6px 9px;
+  border-radius: 5px;
+  font-size: 12px;
+  cursor: pointer;
+  color: var(--fg);
+  box-sizing: border-box;
+}
+.email-filter-item:hover,
+.email-filter-item:focus-visible {
+  background: color-mix(in srgb, var(--fg) 8%, transparent);
+}
+.email-filter-item-icon {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 14px;
+  height: 14px;
+  color: var(--accent, var(--red));
+  flex-shrink: 0;
+}
+.email-filter-item-icon svg { width: 13px; height: 13px; }
+.email-filter-item-label {
+  flex: 1;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
 /* Item metadata row */
 .memory-item-meta {
   display: flex;