Refactor API routes and enhance documentation; add collaboration features and user role management. Update environment example and improve error handling in authentication.

src/app/auth/signin/page.tsx

@@ -40,8 +40,12 @@ export default function SignInPage() {
         router.push("/");
         router.refresh();
       }
-    } catch (error) {
-      setError("An error occurred. Please try again.");
+    } catch (error: unknown) {
+      setError(
+        error instanceof Error
+          ? error.message
+          : "An error occurred. Please try again.",
+      );
     } finally {
       setIsLoading(false);
     }
@@ -108,7 +112,7 @@ export default function SignInPage() {
             </form>
 
             <div className="mt-6 text-center text-sm text-slate-600">
-              Don't have an account?{" "}
+              Don&apos;t have an account?{" "}
               <Link
                 href="/auth/signup"
                 className="font-medium text-blue-600 hover:text-blue-500"