Consolidate hooks

* Hooks are in multiple places in the codebase and some camelCase, some snake-case. This PR relocates them all to the lib/hooks folder and normalizes camelCase naming. Settled on src/client/lib/hooks for the location since most of them were already there.

  - Refactor/move useTheme.ts from client/src/lib to client/src/lib/hooks
  - Refactor/move useToast.ts from client/src/hooks/ to client/src/lib/hooks/useToast.ts
  - Removed client/src/hooks

client/src/lib/hooks/useTheme.ts

@@ -0,0 +1,52 @@
+import { useCallback, useEffect, useMemo, useState } from "react";
+
+type Theme = "light" | "dark" | "system";
+
+const useTheme = (): [Theme, (mode: Theme) => void] => {
+  const [theme, setTheme] = useState<Theme>(() => {
+    const savedTheme = localStorage.getItem("theme") as Theme;
+    return savedTheme || "system";
+  });
+
+  useEffect(() => {
+    const darkModeMediaQuery = window.matchMedia(
+      "(prefers-color-scheme: dark)",
+    );
+    const handleDarkModeChange = (e: MediaQueryListEvent) => {
+      if (theme === "system") {
+        updateDocumentTheme(e.matches ? "dark" : "light");
+      }
+    };
+
+    const updateDocumentTheme = (newTheme: "light" | "dark") => {
+      document.documentElement.classList.toggle("dark", newTheme === "dark");
+    };
+
+    // Set initial theme based on current mode
+    if (theme === "system") {
+      updateDocumentTheme(darkModeMediaQuery.matches ? "dark" : "light");
+    } else {
+      updateDocumentTheme(theme);
+    }
+
+    darkModeMediaQuery.addEventListener("change", handleDarkModeChange);
+
+    return () => {
+      darkModeMediaQuery.removeEventListener("change", handleDarkModeChange);
+    };
+  }, [theme]);
+
+  const setThemeWithSideEffect = useCallback((newTheme: Theme) => {
+    setTheme(newTheme);
+    localStorage.setItem("theme", newTheme);
+    if (newTheme !== "system") {
+      document.documentElement.classList.toggle("dark", newTheme === "dark");
+    }
+  }, []);
+  return useMemo(
+    () => [theme, setThemeWithSideEffect],
+    [theme, setThemeWithSideEffect],
+  );
+};
+
+export default useTheme;