fix: trial balance 1000-row limit and rename /nyckeltal to /kpi (#79)

* fix: trial balance silently truncated at 1000 entries, rename /nyckeltal to /kpi

Trial balance bug:
- The old implementation fetched journal entry IDs (capped at 1000 by
  Supabase default limit), then queried lines via .in(entryIds) which
  also hit URL length limits with large arrays of UUIDs.
- SIE imports create thousands of entries → KPIs showed zero.
- Replaced with a single joined query (journal_entry_lines → journal_entries)
  using fetchAllRows() pagination. No row limit, no URL length issue.
- Removed the non-existent generate_trial_balance RPC call.

Page rename:
- /nyckeltal → /kpi (CLAUDE.md: all code in English)
- Nav label stays "Nyckeltal" (user-facing Swedish UI)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: select filtered columns in joined query, rename component, add redirect

- Select user_id/fiscal_period_id/status from journal_entries!inner()
  so PostgREST applies embedded filters reliably (defense in depth)
- Rename NyckeltalPage → KpiPage per English code convention
- Add permanent /nyckeltal → /kpi redirect for existing bookmarks

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/(dashboard)/kpi/page.tsx

@@ -8,7 +8,7 @@ import { KPIOperationalGrid } from '@/components/kpi/KPIOperationalGrid'
 import { KPITrendChart } from '@/components/kpi/KPITrendChart'
 import type { FiscalPeriod, KPIReport } from '@/types'
 
-export default function NyckeltalPage() {
+export default function KpiPage() {
   const [periods, setPeriods] = useState<FiscalPeriod[]>([])
   const [selectedPeriod, setSelectedPeriod] = useState('')
   const [report, setReport] = useState<KPIReport | null>(null)