feat(board): rework quick-peek modal (Linear-style) + board toolbar

Modal redesign — compact summary instead of two long cards:
- Topbar: breadcrumb + state pill + copyable task-id/link chip; review
  actions (approve / request changes) live in the modal header too
- Main column: title, meta chips (ball, created, last update), compact
  description, then square summary tiles (done/total with progress,
  active, open, blocked) + per-agent pills — details stay in Vollansicht
- Right sidebar: properties as slim Linear-style rows (status, priority,
  assignee, due, source) with hover-reveal controls; activity moved next
  to properties as a compact timeline with a new comment composer
  (POST tasks/{id}/activity via new store action postTaskActivity)
- Unified button system (32px: primary/ghost/approve/changes/icon)
- flattenBoard includes nested children again so quick-peek works for
  child rows inside master cards

Board (issue-tracker basics):
- Toolbar with search (title/detail/id/child titles) and ball filters:
  Alle / Du bist dran / Bei Iris / Haengt

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/components/ui/Badge.vue

@@ -1,11 +1,4 @@
 <script setup lang="ts">
-/**
- * Badge — Nexus V2 Status- und Label-Badge
- *
- * Erweitert: zusätzliche nexus-token-basierte Varianten für
- * Agenten-Rollen, Status-Pills und Prioritäten.
- * Original shadcn-Varianten bleiben erhalten.
- */
 import type { HTMLAttributes } from 'vue'
 import { cva, type VariantProps } from 'class-variance-authority'
 import { cn } from '@/lib/utils'
@@ -15,25 +8,10 @@ const badgeVariants = cva(
   {
     variants: {
       variant: {
-        // Original shadcn
         default: 'border-transparent bg-primary text-primary-foreground shadow hover:bg-primary/80',
         secondary: 'border-transparent bg-secondary text-secondary-foreground hover:bg-secondary/80',
         destructive: 'border-transparent bg-destructive text-destructive-foreground shadow hover:bg-destructive/80',
         outline: 'text-foreground',
-
-        // Nexus V2 — Token-basierte Varianten (Farben aus nexus-tokens.css)
-        work: 'nexus-badge-work',
-        think: 'nexus-badge-think',
-        blocked: 'nexus-badge-blocked',
-        queue: 'nexus-badge-queue',
-        done: 'nexus-badge-done',
-        review: 'nexus-badge-review',
-        iris: 'nexus-badge-iris',
-        bao: 'nexus-badge-bao',
-        agent: 'nexus-badge-agent',
-        priorityHigh: 'nexus-badge-prio-high',
-        priorityMed: 'nexus-badge-prio-med',
-        priorityLow: 'nexus-badge-prio-low',
       },
     },
     defaultVariants: {
@@ -57,78 +35,3 @@ const props = withDefaults(defineProps<Props>(), {
     <slot />
   </span>
 </template>
-
-<style scoped>
-/* Nexus V2 Token-basierte Badge-Varianten */
-.nexus-badge-work {
-  border-color: rgba(61, 220, 151, .25);
-  background: rgba(34, 197, 94, .12);
-  color: var(--st-work);
-}
-
-.nexus-badge-think {
-  border-color: rgba(52, 214, 245, .25);
-  background: rgba(52, 214, 245, .1);
-  color: var(--st-think);
-}
-
-.nexus-badge-blocked {
-  border-color: rgba(251, 113, 133, .25);
-  background: rgba(244, 63, 94, .12);
-  color: var(--st-block);
-}
-
-.nexus-badge-queue {
-  border-color: rgba(251, 191, 36, .25);
-  background: rgba(251, 191, 36, .12);
-  color: var(--st-queue);
-}
-
-.nexus-badge-done {
-  border-color: rgba(34, 197, 94, .25);
-  background: rgba(34, 197, 94, .12);
-  color: var(--st-work);
-}
-
-.nexus-badge-review {
-  border-color: rgba(249, 115, 22, .25);
-  background: rgba(249, 115, 22, .12);
-  color: var(--clr-review);
-}
-
-.nexus-badge-iris {
-  border-color: rgba(147, 51, 234, .25);
-  background: rgba(147, 51, 234, .12);
-  color: var(--clr-iris);
-}
-
-.nexus-badge-bao {
-  border-color: rgba(59, 130, 246, .25);
-  background: rgba(59, 130, 246, .12);
-  color: var(--clr-bao);
-}
-
-.nexus-badge-agent {
-  border-color: rgba(16, 185, 129, .2);
-  background: rgba(16, 185, 129, .12);
-  color: var(--clr-agent);
-}
-
-.nexus-badge-prio-high {
-  border-color: var(--st-block);
-  background: transparent;
-  color: var(--st-block);
-}
-
-.nexus-badge-prio-med {
-  border-color: var(--st-queue);
-  background: transparent;
-  color: var(--st-queue);
-}
-
-.nexus-badge-prio-low {
-  border-color: var(--a-blue);
-  background: transparent;
-  color: var(--a-blue);
-}
-</style>