feat: Add loot builder frontend — Pinia store, views, 4 components, router + nav

Implements the complete frontend for BetterLoot profile management:
- Pinia store (loot.ts) with CRUD, import/export, apply-to-server actions
- LootBuilderView orchestrator with profile bar, modals, two-column layout
- LootContainerSidebar with categorized container list, search, config indicators
- LootItemEditor for per-container item settings and ungrouped item table
- LootItemPicker modal with searchable/filterable Rust item grid
- LootGroupEditor for reusable loot group management
- Router integration at /loot-builder
- Sidebar nav item with Crosshair icon and loot.view permission

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/loot/LootContainerSidebar.vue

@@ -0,0 +1,103 @@
+<script setup lang="ts">
+import { ref, computed } from 'vue'
+import { rustContainers, containerCategories } from '@/data/rust-containers'
+import { Search, Box, Cylinder, Shield, Users, HelpCircle } from 'lucide-vue-next'
+
+const props = defineProps<{
+  lootTable: Record<string, any>
+  selected: string | null
+}>()
+
+const emit = defineEmits<{
+  select: [prefab: string]
+}>()
+
+const searchQuery = ref('')
+
+const categoryIcons: Record<string, any> = {
+  crates: Box,
+  barrels: Cylinder,
+  military: Shield,
+  npcs: Users,
+  other: HelpCircle,
+}
+
+const categoryLabels: Record<string, string> = {
+  crates: 'CRATES',
+  barrels: 'BARRELS',
+  military: 'MILITARY',
+  npcs: 'NPCs',
+  other: 'OTHER',
+}
+
+const filteredContainers = computed(() => {
+  const q = searchQuery.value.toLowerCase()
+  if (!q) return rustContainers
+  return rustContainers.filter(c => c.name.toLowerCase().includes(q) || c.prefab.toLowerCase().includes(q))
+})
+
+const groupedContainers = computed(() => {
+  const groups: Record<string, typeof rustContainers> = {}
+  for (const cat of containerCategories) {
+    const items = filteredContainers.value.filter(c => c.category === cat)
+    if (items.length > 0) groups[cat] = items
+  }
+  return groups
+})
+
+function isConfigured(prefab: string): boolean {
+  const entry = props.lootTable[prefab]
+  if (!entry) return false
+  const hasItems = entry.UngroupedItems && Object.keys(entry.UngroupedItems).length > 0
+  const hasGuaranteed = entry.GuaranteedItems && Object.keys(entry.GuaranteedItems).length > 0
+  const hasProfiles = entry.LootProfiles && entry.LootProfiles.length > 0
+  return hasItems || hasGuaranteed || hasProfiles
+}
+</script>
+
+<template>
+  <div class="w-64 shrink-0 bg-neutral-900 border border-neutral-800 rounded-xl overflow-hidden flex flex-col">
+    <!-- Search -->
+    <div class="p-3 border-b border-neutral-800">
+      <div class="relative">
+        <Search class="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-neutral-500" />
+        <input
+          v-model="searchQuery"
+          placeholder="Search containers..."
+          class="w-full bg-neutral-800 border border-neutral-700 rounded-lg pl-9 pr-3 py-2 text-sm text-neutral-200 placeholder-neutral-500"
+        />
+      </div>
+    </div>
+
+    <!-- Container List -->
+    <div class="flex-1 overflow-y-auto py-2">
+      <template v-for="(containers, category) in groupedContainers" :key="category">
+        <div class="px-3 pt-3 pb-1">
+          <div class="flex items-center gap-2 text-[10px] font-semibold uppercase tracking-widest text-neutral-500">
+            <component :is="categoryIcons[category]" class="w-3 h-3" />
+            {{ categoryLabels[category] || category }}
+          </div>
+        </div>
+        <button
+          v-for="c in containers"
+          :key="c.prefab"
+          @click="emit('select', c.prefab)"
+          class="w-full text-left px-3 py-1.5 text-sm flex items-center gap-2 transition-colors"
+          :class="selected === c.prefab
+            ? 'bg-oxide-500/10 text-oxide-400'
+            : 'text-neutral-400 hover:bg-neutral-800 hover:text-neutral-200'"
+        >
+          <span class="truncate flex-1">{{ c.name }}</span>
+          <span
+            v-if="isConfigured(c.prefab)"
+            class="w-1.5 h-1.5 rounded-full bg-oxide-500 shrink-0"
+          />
+        </button>
+      </template>
+
+      <div v-if="Object.keys(groupedContainers).length === 0" class="px-3 py-6 text-center text-neutral-500 text-sm">
+        No containers match
+      </div>
+    </div>
+  </div>
+</template>