improvement: rtl direction, solar calendar and persian formatting added for persian users.

frontend/src/styles/globals.css

@@ -241,10 +241,34 @@ html[data-theme='light'] {
   color-scheme: light;
 }
 
+/* Minimal RTL layer — refine incrementally. */
+html[dir='rtl'] body {
+  direction: rtl;
+}
+
+/* Sidebar: don't rely on Tailwind rtl: variants. */
+html[dir='rtl'] .app-sidebar {
+  border-right: 0;
+  border-left: 1px solid var(--color-border);
+}
+
+/* Mobile drawer only — desktop sidebar follows flex + document direction. */
+@media (max-width: 1023px) {
+  html[dir='rtl'] .app-sidebar {
+    left: auto;
+    right: 0;
+  }
+}
+
+/* Treatment rail: align header text to the right in RTL. */
+html[dir='rtl'] .treatment-rail-section > button {
+  text-align: right;
+}
+
 body {
   background-color: var(--color-background-primary);
   color: var(--color-text-primary);
-  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
+  font-family: var(--font-sans, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif);
 }
 
 select.form-select,
@@ -254,6 +278,25 @@ select {
   font-size: 1rem;
 }
 
+/* Shared chevron for all `.form-select` — symmetric inset matches `ps-3` text padding. */
+select.form-select:not(.form-select-no-chevron) {
+  appearance: none;
+  -webkit-appearance: none;
+  text-align: start;
+  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
+  background-repeat: no-repeat;
+  background-size: 1rem 1rem;
+  background-position: right 0.75rem center;
+}
+
+html[dir='rtl'] select.form-select:not(.form-select-no-chevron) {
+  background-position: left 0.75rem center;
+}
+
+select.form-select.form-select-no-chevron {
+  background-image: none;
+}
+
 @media (min-width: 640px) {
   select.form-select,
   select {