fix: add 404 not found page (#349)

* fix: add 404 not found page

Closes #320

- Add custom 404 page matching the app's design system
- Include PatternedBackground and proper dark mode support
- Provide navigation links to homepage and boards
- Add i18n support with @lingui/react

* fix: add 404 redirects for non-existent boards and cards

Add useEffect hooks to redirect to /404 page when:
- Board does not exist in board view
- Card does not exist in card view

This addresses the cases mentioned in maintainer feedback where
the static 404 page wasn't being used for dynamic routes.

Addresses review feedback on PR #349

* feat: redirect to 404 for non-existent public workspaces and cards

Per maintainer feedback:
- Add redirect logic to public boards view when workspace doesn't exist
- Add redirect logic to public card modal when card doesn't exist
- Uses error?.data?.code === 'NOT_FOUND' check as suggested
- Closes modal before redirecting for card modal

apps/web/src/views/board/index.tsx

@@ -125,11 +125,21 @@ export default function BoardPage({ isTemplate }: { isTemplate?: boolean }) {
     data: boardData,
     isSuccess,
     isLoading: isQueryLoading,
+    error,
   } = api.board.byId.useQuery(queryParams, {
     enabled: !!boardId,
     placeholderData: keepPreviousData,
   });
 
+  // Redirect to 404 if board doesn't exist
+  useEffect(() => {
+    if (router.isReady && boardId && !isQueryLoading) {
+      if (error?.data?.code === "NOT_FOUND" || (!boardData && !isQueryLoading)) {
+        router.replace("/404");
+      }
+    }
+  }, [router, boardId, isQueryLoading, error, boardData]);
+
   const refetchBoard = async () => {
     if (boardId) await utils.board.byId.refetch({ boardPublicId: boardId });
   };

apps/web/src/views/card/index.tsx

@@ -185,11 +185,20 @@ export default function CardPage({ isTemplate }: { isTemplate?: boolean }) {
     ? router.query.cardId[0]
     : router.query.cardId;
 
-  const { data: card, isLoading } = api.card.byId.useQuery(
+  const { data: card, isLoading, error } = api.card.byId.useQuery(
     { cardPublicId: cardId ?? "" },
     { enabled: !!cardId && cardId.length >= 12 },
   );
 
+  // Redirect to 404 if card doesn't exist
+  useEffect(() => {
+    if (router.isReady && cardId && !isLoading) {
+      if (error?.data?.code === "NOT_FOUND" || (!card && !isLoading)) {
+        router.replace("/404");
+      }
+    }
+  }, [router, cardId, isLoading, error, card]);
+
   const isCreator = card?.createdBy && session?.user.id === card.createdBy;
   const canEdit = canEditCard || isCreator;
 

apps/web/src/views/public/board/CardModal.tsx

@@ -47,7 +47,7 @@ export function CardModal({
     }
   };
 
-  const { data, isLoading } = api.card.byId.useQuery(
+  const { data, isLoading, error } = api.card.byId.useQuery(
     {
       cardPublicId: cardPublicId ?? "",
     },
@@ -56,6 +56,17 @@ export function CardModal({
     },
   );
 
+  // Redirect to 404 if card doesn't exist
+  useEffect(() => {
+    if (isOpen && cardPublicId && !isLoading) {
+      if (error?.data?.code === "NOT_FOUND" || (!data && !isLoading && error)) {
+        // Close modal first, then redirect
+        closeModal();
+        router.replace("/404");
+      }
+    }
+  }, [isOpen, cardPublicId, isLoading, error, data, closeModal, router]);
+
   const labels = data?.labels ?? [];
 
   const handleScroll = () => {

apps/web/src/views/public/boards/index.tsx

@@ -1,5 +1,6 @@
 import Link from "next/link";
 import { useRouter } from "next/router";
+import { useEffect } from "react";
 import { t } from "@lingui/core/macro";
 import { PageHead } from "~/components/PageHead";
 import PatternedBackground from "~/components/PatternedBackground";
@@ -12,13 +13,22 @@ export default function PublicBoardsView() {
     ? router.query.workspaceSlug[0]
     : router.query.workspaceSlug;
 
-  const { data, isLoading } = api.workspace.bySlug.useQuery(
+  const { data, isLoading, error } = api.workspace.bySlug.useQuery(
     {
       workspaceSlug: workspaceSlug ?? "",
     },
     { enabled: !!workspaceSlug },
   );
 
+  // Redirect to 404 if workspace doesn't exist
+  useEffect(() => {
+    if (router.isReady && workspaceSlug && !isLoading) {
+      if (error?.data?.code === "NOT_FOUND" || (!data && !isLoading)) {
+        router.replace("/404");
+      }
+    }
+  }, [router, workspaceSlug, isLoading, error, data]);
+
   const BoardsList = ({
     isLoading,
     boards,