feat: OpenAI compatibility improvements & build fixes

- Fix hydration mismatches and initialization errors
- Add /v1/models endpoint for OpenAI clients
- Add Codex response translator (Responses → OpenAI)
- Fix circular dependencies and PropTypes
- Add Material Symbols font and CSS fixes
- Update README with deployment guide

Co-merged from PR #18 (14/15 commits, skipped debug)

src/shared/hooks/useTheme.js

@@ -1,31 +1,60 @@
 "use client";
 
-import { useEffect } from "react";
+import { useEffect, useState, useSyncExternalStore } from "react";
 import useThemeStore from "@/store/themeStore";
 
+// Subscribe to system theme changes
+function subscribeToSystemTheme(callback) {
+  if (typeof window === "undefined") return () => {};
+  const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
+  mediaQuery.addEventListener("change", callback);
+  return () => mediaQuery.removeEventListener("change", callback);
+}
+
+// Get current system theme preference
+function getSystemThemeSnapshot() {
+  if (typeof window === "undefined") return false;
+  return window.matchMedia("(prefers-color-scheme: dark)").matches;
+}
+
+// Server snapshot always returns false
+function getServerSnapshot() {
+  return false;
+}
+
 export function useTheme() {
   const { theme, setTheme, toggleTheme, initTheme } = useThemeStore();
 
+  // Use useSyncExternalStore to safely subscribe to system theme
+  const systemPrefersDark = useSyncExternalStore(
+    subscribeToSystemTheme,
+    getSystemThemeSnapshot,
+    getServerSnapshot
+  );
+
   useEffect(() => {
     initTheme();
+  }, [initTheme]);
+
+  // Listen for system theme changes when theme is "system"
+  useEffect(() => {
+    if (theme !== "system") return;
 
-    // Listen for system theme changes
     const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)");
-    const handleChange = () => {
-      if (theme === "system") {
-        initTheme();
-      }
-    };
+    const handleChange = () => initTheme();
 
     mediaQuery.addEventListener("change", handleChange);
     return () => mediaQuery.removeEventListener("change", handleChange);
   }, [theme, initTheme]);
 
+  // Compute isDark from current state (no effect needed)
+  const isDark = theme === "dark" || (theme === "system" && systemPrefersDark);
+
   return {
     theme,
     setTheme,
     toggleTheme,
-    isDark: theme === "dark" || (theme === "system" && typeof window !== "undefined" && window.matchMedia("(prefers-color-scheme: dark)").matches),
+    isDark,
   };
 }