feat: transaction categorization UX improvements and description matching

Add journal entry preview, human-readable account names, auto-apply VAT,
fallback template suggestions, example prompts, invoice match comparison,
and batch result feedback. Also includes user-description-match extension,
describe/batch-describe API routes, improved AI categorization with multi-
suggestion support, and template embedding search.

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

extensions/general/user-description-match/index.ts

@@ -0,0 +1,142 @@
+import type { Extension, ExtensionContext } from '@/lib/extensions/types'
+import type { EventPayload } from '@/lib/events/types'
+
+// ============================================================
+// Settings
+// ============================================================
+
+export interface UserDescriptionMatchSettings {
+  batchApplyEnabled: boolean
+  minConfidenceThreshold: number
+}
+
+const DEFAULT_SETTINGS: UserDescriptionMatchSettings = {
+  batchApplyEnabled: true,
+  minConfidenceThreshold: 0.55,
+}
+
+export async function getSettings(userId: string): Promise<UserDescriptionMatchSettings> {
+  const { createClient } = await import('@/lib/supabase/server')
+  const supabase = await createClient()
+
+  const { data } = await supabase
+    .from('extension_data')
+    .select('value')
+    .eq('user_id', userId)
+    .eq('extension_id', 'user-description-match')
+    .eq('key', 'settings')
+    .single()
+
+  if (!data?.value) return { ...DEFAULT_SETTINGS }
+  return { ...DEFAULT_SETTINGS, ...(data.value as Partial<UserDescriptionMatchSettings>) }
+}
+
+export async function saveSettings(
+  userId: string,
+  partial: Partial<UserDescriptionMatchSettings>
+): Promise<UserDescriptionMatchSettings> {
+  const current = await getSettings(userId)
+  const merged = { ...current, ...partial }
+
+  const { createClient } = await import('@/lib/supabase/server')
+  const supabase = await createClient()
+
+  await supabase
+    .from('extension_data')
+    .upsert(
+      {
+        user_id: userId,
+        extension_id: 'user-description-match',
+        key: 'settings',
+        value: merged,
+      },
+      { onConflict: 'user_id,extension_id,key' }
+    )
+
+  return merged
+}
+
+// ============================================================
+// Event Handler
+// ============================================================
+
+async function handleTransactionCategorized(
+  payload: EventPayload<'transaction.categorized'>,
+  ctx?: ExtensionContext
+): Promise<void> {
+  const { transaction, userId } = payload
+  const log = ctx?.log ?? console
+
+  if (!transaction.merchant_name) return
+
+  const settings = ctx
+    ? { ...(DEFAULT_SETTINGS), ...(await ctx.settings.get<Partial<UserDescriptionMatchSettings>>() || {}) }
+    : await getSettings(userId)
+
+  if (!settings.batchApplyEnabled) return
+
+  try {
+    const supabase = ctx?.supabase ?? await (await import('@/lib/supabase/server')).createClient()
+
+    // Check if the rule that fired was a user-described rule
+    const { data: rule } = await supabase
+      .from('mapping_rules')
+      .select('id, user_description, merchant_pattern')
+      .eq('user_id', userId)
+      .eq('source', 'user_description')
+      .ilike('merchant_pattern', transaction.merchant_name.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'))
+      .limit(1)
+      .single()
+
+    if (!rule) return
+
+    // Count uncategorized siblings
+    const { count } = await supabase
+      .from('transactions')
+      .select('id', { count: 'exact', head: true })
+      .eq('user_id', userId)
+      .eq('merchant_name', transaction.merchant_name)
+      .is('journal_entry_id', null)
+
+    if (!count || count === 0) return
+
+    // Store batch hint for the UI
+    await supabase.from('extension_data').upsert(
+      {
+        user_id: userId,
+        extension_id: 'user-description-match',
+        key: `batch_hint:${transaction.merchant_name}`,
+        value: {
+          merchant_name: transaction.merchant_name,
+          uncategorized_count: count,
+          user_description: rule.user_description,
+        },
+      },
+      { onConflict: 'user_id,extension_id,key' }
+    )
+
+    log.info(`[user-description-match] Batch hint stored: ${count} uncategorized for ${transaction.merchant_name}`)
+  } catch (error) {
+    log.error('[user-description-match] handleTransactionCategorized failed:', error)
+  }
+}
+
+// ============================================================
+// Extension Object
+// ============================================================
+
+export const userDescriptionMatchExtension: Extension = {
+  id: 'user-description-match',
+  name: 'Beskrivningsmatchning',
+  version: '1.0.0',
+  eventHandlers: [
+    { eventType: 'transaction.categorized', handler: handleTransactionCategorized },
+  ],
+  settingsPanel: {
+    label: 'Beskrivningsmatchning',
+    path: '/settings/extensions/user-description-match',
+  },
+  async onInstall(ctx) {
+    await ctx.settings.set('settings', DEFAULT_SETTINGS)
+  },
+}