feat: add theme system, fonts, graph styling, rename Overview→Tasks

- Terracotta (light) and Carbon (dark) themes with toggle
- Inknut Antiqua headings, DM Sans body
- Dot grid background on EntityGraph and GraphBackground
- Theme-adaptive graph colors on EntityGraph
- Art Nouveau chat styling (borders, underlines, blockquote quotes)
- Bullet point styles in chat prose
- Task goal in header, rename Overview→Tasks, New Task labels
- Logo uses var(--primary) for theme awareness

web/src/App.svelte

@@ -11,6 +11,7 @@
   import { newChat } from '$lib/stores/chat'
   import { summary, subscribeContext, openSignalCount } from '$lib/stores/context'
   import { connectionState } from '$lib/stores/events'
+  import { currentTask } from '$lib/stores/workspace'
   import { isConfigured } from '$lib/config'
   import { onMount } from 'svelte'
   import { processPendingCallback, initOIDC } from '$lib/oidc'
@@ -22,7 +23,7 @@
   import { VERSION } from '$lib/version'
   import { Toaster } from '$lib/components/ui/sonner'
   import PlusIcon from '@lucide/svelte/icons/plus'
-  import LayoutDashboardIcon from '@lucide/svelte/icons/layout-dashboard'
+  import ListTodoIcon from '@lucide/svelte/icons/list-todo'
   import DatabaseIcon from '@lucide/svelte/icons/database'
   import PanelRightIcon from '@lucide/svelte/icons/panel-right'
   import ShieldCheckIcon from '@lucide/svelte/icons/shield-check'
@@ -30,6 +31,8 @@
   import SearchIcon from '@lucide/svelte/icons/search'
   import TrendingUpIcon from '@lucide/svelte/icons/trending-up'
   import SettingsIcon from '@lucide/svelte/icons/settings'
+  import PaletteIcon from '@lucide/svelte/icons/palette'
+  import { getTheme, toggleTheme, THEME_LABELS } from '$lib/stores/theme.svelte'
 
   let page = $state('overview')
   let routeParam = $state('')
@@ -73,8 +76,12 @@
     location.hash = '#/' + p
   }
 
+  function cycleTheme() {
+    toggleTheme()
+  }
+
   const navItems = [
-    { id: 'overview', label: 'Overview', icon: LayoutDashboardIcon },
+    { id: 'overview', label: 'Tasks', icon: ListTodoIcon },
     { id: 'kb', label: 'Knowledge Base', icon: DatabaseIcon },
     { id: 'ops', label: 'Operations', icon: ShieldCheckIcon, badge: () => approvalsPending },
     { id: 'signals', label: 'Signals', icon: SirenIcon, badge: () => openSignals },
@@ -104,7 +111,7 @@
           >
             {#snippet child({ props })}
               <button {...props}>
-                <svg viewBox="0 0 91 100" class="!size-5 shrink-0 fill-white" aria-hidden="true" role="img">
+                <svg viewBox="0 0 91 100" class="!size-5 shrink-0" fill="var(--primary)" aria-hidden="true" role="img">
                   <title>Oikos</title>
                   <path d="m45.601 1q20.993 0 33.71 15.946 10.799 13.625 10.799 31.287 0 12.414-5.9548 25.131-5.9548 12.717-16.451 19.176-10.395 6.4592-23.213 6.4592-20.892 0-33.205-16.653-10.395-14.029-10.395-31.489 0-12.717 6.2577-25.232 6.3584-12.616 16.653-18.57 10.295-6.0556 21.801-6.0556zm-3.128 6.5605q-5.3492 0-10.799 3.2296-5.3492 3.1287-8.68 11.102-3.3305 7.9735-3.3305 20.488 0 20.185 7.973 34.82 8.0743 14.634 21.195 14.634 9.7896 0 16.149-8.0743 6.3584-8.0743 6.3584-27.755 0-24.627-10.597-38.756-7.1657-9.6888-18.268-9.6888z" />
                 </svg>
@@ -171,6 +178,16 @@
         <PanelRightIcon />
         <span>Chat drawer</span>
       </Button>
+      <Button
+        variant="ghost"
+        size="sm"
+        class="justify-start gap-2"
+        onclick={cycleTheme}
+        title="Cycle theme"
+      >
+        <PaletteIcon />
+        <span>{THEME_LABELS[getTheme()]}</span>
+      </Button>
       <Button
         variant="ghost"
         size="sm"
@@ -189,11 +206,13 @@
       <Sidebar.Trigger class="-ms-1" />
       <Separator orientation="vertical" class="mx-2 data-[orientation=vertical]:h-4" />
       {#if page === 'chat'}
-        <button type="button" class="text-sm text-muted-foreground hover:text-foreground" onclick={() => navigate('overview')}>Overview</button>
+        <button type="button" class="text-sm text-muted-foreground hover:text-foreground" onclick={() => navigate('overview')}>Tasks</button>
         <span class="text-muted-foreground">/</span>
-        <span class="text-base font-medium">Conversation</span>
+        <span class="text-base font-medium">
+          {$currentTask?.goal ? $currentTask.goal.replace(/[*_`~#]|\[.*?\]\(.*?\)/g, '') : 'New Task'}
+        </span>
       {:else}
-        <span class="text-base font-medium capitalize">{page === 'entity' ? routeParam : page === 'kb' ? 'Knowledge Base' : page}</span>
+        <span class="text-base font-medium capitalize">{page === 'entity' ? routeParam : page === 'kb' ? 'Knowledge Base' : page === 'overview' ? 'Tasks' : page}</span>
       {/if}
       <div class="ms-auto flex items-center gap-2.5">
       {#if $summary}