feat(backend,frontend): search everywhere in buttons, links and message data, a jump from search or an alert lights up the found words and buttons

frontend/src/lib/components/EntityText.svelte

@@ -8,14 +8,16 @@
     jumboEmojiCount,
     linkHref,
   } from "#lib/format/entities.js";
+  import { markText } from "#lib/format/search.js";
 
   interface Props {
     entities: EntityView[];
+    marks?: string[];
     own?: boolean;
     text: string;
   }
 
-  let { text, entities, own = false }: Props = $props();
+  let { text, entities, marks = [], own = false }: Props = $props();
 
   const nodes = $derived(buildEntityTree(text, entities));
   const jumbo = $derived(entities.length === 0 ? jumboEmojiCount(text) : 0);
@@ -32,13 +34,29 @@
 )}
   {#each items as node, i (i)}
     {#if node.kind === "text"}
-      {node.text}
+      {@render plain(node.text)}
     {:else}
       {@render entity(node)}
     {/if}
   {/each}
 {/snippet}
 
+{#snippet plain(
+  value: string
+)}
+  {#if marks.length === 0}
+    {value}
+  {:else}
+    {#each markText(value, marks) as segment, i (i)}
+      {#if segment.hit}
+        <mark class="found" class:own>{segment.text}</mark>
+      {:else}
+        {segment.text}
+      {/if}
+    {/each}
+  {/if}
+{/snippet}
+
 {#snippet entity(
   node: EntityNode
 )}
@@ -186,6 +204,35 @@
     background-color: var(--color-primary-tint);
   }
 
+  .found {
+    padding: 0;
+    border-radius: 0.25rem;
+    color: inherit;
+    background-color: transparent;
+    animation: found-flash 3s ease;
+
+    --found-color: color-mix(in srgb, var(--color-primary) 40%, transparent);
+
+    &.own {
+      --found-color: color-mix(
+        in srgb,
+        var(--color-own-links) 35%,
+        transparent
+      );
+    }
+  }
+
+  @keyframes found-flash {
+    0%,
+    70% {
+      background-color: var(--found-color);
+    }
+
+    100% {
+      background-color: transparent;
+    }
+  }
+
   .spoiler {
     cursor: pointer;