Bookmarks on public/semi activities, surfaced on /home

Logged-in users can star a public or semi activity to save it for
later. Bookmarked rows float to the top of the user's dashboard in a
dedicated "Bokmerker" section. The same row still appears in its
visibility section below — bookmarking doesn't remove anything; it
just adds a fast lane.

Schema:
  - bookmarks(user_id, activity_id, created_at) with composite PK
  - Both FKs CASCADE so user deletion or activity deletion sweeps
    bookmarks automatically

Wire/types: ActivityPublic/Semi/Private all gain `viewer_bookmarked:
boolean` for type uniformity. Private rows always carry false (the
owner already has direct access; bookmarking own private items would
be redundant), and the bookmark endpoints reject visibility='private'
with cannot_bookmark_private. Anonymous viewers (public-list endpoint)
get false too.

Server:
  - viewerBookmarked() helper next to heartsFor() — same shape
  - serialize() includes the field
  - POST/DELETE /api/activities/:id/bookmark, idempotent via
    INSERT OR IGNORE / DELETE; mirrors the heart endpoints

Frontend:
  - ActivityRow gets an "☆ Bokmerk" / "★ Bokmerket" toggle next to
    the heart button. Uses the same optimistic local-override pattern
    so the UI feels instant.
  - Home renders a "Bokmerker" section at the top when bookmarked
    rows exist. publicOnly mode (the "/" landing) skips it — the
    field is always false there.

26 tests still pass; typecheck clean.

frontend/src/components/ActivityRow.svelte

@@ -133,13 +133,33 @@
       localOverride = updated;
       onChanged?.(updated);
     } catch {
-      // Snap back.
       localOverride = null;
     } finally {
       heartBusy = false;
     }
   }
 
+  // --- Bookmarks -----------------------------------------------------------
+  let bookmarkBusy = $state(false);
+  async function toggleBookmark() {
+    if (!session.user || bookmarkBusy) return;
+    if (view.visibility === 'private') return;
+    bookmarkBusy = true;
+    const wasBookmarked = view.viewer_bookmarked;
+    localOverride = { ...view, viewer_bookmarked: !wasBookmarked };
+    try {
+      const updated = wasBookmarked
+        ? await api.unbookmarkActivity(view.id)
+        : await api.bookmarkActivity(view.id);
+      localOverride = updated;
+      onChanged?.(updated);
+    } catch {
+      localOverride = null;
+    } finally {
+      bookmarkBusy = false;
+    }
+  }
+
   /**
    * Share-link: copy /a/<id> (absolute URL) to the clipboard. Private rows
    * are shareable in principle but only the owner can decrypt — the receiver
@@ -242,6 +262,16 @@
         >
           {view.viewer_hearted ? '♥' : '♡'} {view.heart_count}
         </button>
+        <button
+          type="button"
+          onclick={toggleBookmark}
+          disabled={bookmarkBusy}
+          aria-pressed={view.viewer_bookmarked}
+          aria-label={view.viewer_bookmarked ? 'Fjern bokmerke' : 'Bokmerk'}
+          title={view.viewer_bookmarked ? 'Fjern bokmerke' : 'Bokmerk'}
+        >
+          {view.viewer_bookmarked ? '★ Bokmerket' : '☆ Bokmerk'}
+        </button>
       {:else if view.heart_count > 0}
         <span class="muted" aria-label="Antall hjerter">♡ {view.heart_count}</span>
       {/if}

frontend/src/components/Home.svelte

@@ -102,8 +102,17 @@
       .filter((a) => matchesQuery(a, query)),
   );
 
-  // Split into the three sections defined in the spec — "mine privat" first,
-  // then anonyme, then offentlige.
+  // Split into sections. Bookmarks float to the top (only for logged-in users
+  // looking at their full dashboard — public landing skips them since the
+  // viewer_bookmarked field is always false there). The bookmark itself
+  // doesn't remove the activity from its visibility section — the same row
+  // appears once in "Bokmerker" AND once in its semi/public section so you
+  // can still find it where you'd expect.
+  const bookmarked = $derived(
+    publicOnly || !session.user
+      ? []
+      : filtered.filter((a) => a.visibility !== 'private' && a.viewer_bookmarked),
+  );
   const myPrivate = $derived(filtered.filter((a) => a.visibility === 'private'));
   const semi      = $derived(filtered.filter((a) => a.visibility === 'semi'));
   const pub       = $derived(filtered.filter((a) => a.visibility === 'public'));
@@ -160,6 +169,19 @@
   {:else if error}
     <p class="error">{error}</p>
   {:else}
+    {#if bookmarked.length}
+      <h2>Bokmerker</h2>
+      {#each bookmarked as a (a.id)}
+        <ActivityRow
+          activity={a}
+          privateCleartext={null}
+          onDeleted={onDeleted}
+          onEdit={(act) => (editing = act)}
+          onChanged={onChanged}
+        />
+      {/each}
+    {/if}
+
     {#if myPrivate.length}
       <h2>Dine private</h2>
       {#each myPrivate as a (a.id)}

frontend/src/lib/api.ts

@@ -78,6 +78,10 @@ export const api = {
     http<Activity>(`/activities/${encodeURIComponent(id)}/heart`, { method: 'POST' }),
   unheartActivity: (id: string) =>
     http<Activity>(`/activities/${encodeURIComponent(id)}/heart`, { method: 'DELETE' }),
+  bookmarkActivity: (id: string) =>
+    http<Activity>(`/activities/${encodeURIComponent(id)}/bookmark`, { method: 'POST' }),
+  unbookmarkActivity: (id: string) =>
+    http<Activity>(`/activities/${encodeURIComponent(id)}/bookmark`, { method: 'DELETE' }),
 
   // --- tags -----------------------------------------------------------------
   tagSuggestions: (q: string, limit = 20) =>