feat: Journal list, category pages, pagination, tokens and pl/en strings

- index and category pages paginate with ?page=N and 404 out of range
- category content renders above the list through the html gate
- related posts fall back to the latest posts
- --journal-* tokens and neutral base styles
- pl/en strings registered only for locales the app enables

app/utils/pagination.ts

@@ -0,0 +1,36 @@
+// Page-number rules for Journal listings. Pages use ?page=N (never a path
+// segment). Anything but a positive integer, and any page past the last one,
+// is a real 404.
+
+/**
+ * Parses the ?page query value: 1 when absent, the integer for a string of
+ * digits greater than 0, and null (a 404) for anything else: non-numeric,
+ * empty, 0, negative, decimal, repeated (array) or beyond the safe range.
+ */
+export function parsePageParam(raw: unknown): number | null {
+  if (raw === undefined || raw === null) return 1
+  if (typeof raw !== 'string' || !/^\d+$/.test(raw)) return null
+  const n = Number(raw)
+  if (!Number.isSafeInteger(n) || n < 1) return null
+  return n
+}
+
+/**
+ * True when `page` lies past the last page. Page 1 is always in range, so an
+ * empty listing renders its empty state instead of a 404.
+ */
+export function pageOutOfRange(page: number, lastPage: number): boolean {
+  return page > 1 && page > lastPage
+}
+
+/**
+ * The page numbers to render around `current`: at most `size` consecutive
+ * pages, clipped to 1..last and kept full-width near either end.
+ */
+export function paginationWindow(current: number, last: number, size: number = 5): number[] {
+  if (last < 1 || size < 1) return []
+  const width = Math.min(size, last)
+  let start = Math.max(1, current - Math.floor(width / 2))
+  if (start + width - 1 > last) start = last - width + 1
+  return Array.from({ length: width }, (_, i) => start + i)
+}

app/utils/view.ts

@@ -16,6 +16,22 @@ export interface JournalPostView extends JournalPostDetail {
   content_blocked: boolean
 }
 
+/**
+ * Formats an API timestamp as a long date for `language` (a BCP 47 tag such
+ * as "pl-PL"). UTC on both server and browser, so hydration matches. Returns
+ * "" for a missing or invalid value.
+ */
+export function formatJournalDate(iso: string | null | undefined, language: string): string {
+  if (!iso) return ''
+  const d = new Date(iso)
+  if (Number.isNaN(d.getTime())) return ''
+  try {
+    return new Intl.DateTimeFormat(language || 'en', { dateStyle: 'long', timeZone: 'UTC' }).format(d)
+  } catch {
+    return new Intl.DateTimeFormat('en', { dateStyle: 'long', timeZone: 'UTC' }).format(d)
+  }
+}
+
 export function toPostView(post: JournalPostDetail): JournalPostView {
   const gated = gateJournalHtml(post.content_html)
   return {