fix(reports): always emit compulsory #FORMAT PC8 in SIE export (#1466)

#FORMAT is a compulsory record in every SIE type and PC8 is its only
legal value. We only emitted it when the caller opted into cp437 byte
encoding, so the default UTF-8 download had no #FORMAT line and strict
importers (Visma Spiris) rejected the file with 'Etiketten #FORMAT
saknas i filen'. Cloud exporters (Fortnox, Bokio) ship UTF-8 bytes with
#FORMAT PC8 and importers detect the real encoding from the bytes, so
the tag is now unconditional.

Also formats #ORGNR as nnnnnn-nnnn per spec; company_settings stores
the org number without a hyphen.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/reports/__tests__/sie-export.test.ts

@@ -97,13 +97,32 @@ describe('generateSIEExport', () => {
     const lines = output.split('\r\n')
 
     expect(lines[0]).toBe('#FLAGGA 0')
-    expect(lines[1]).toBe('#SIETYP 4')
-    expect(lines[2]).toMatch(/^#PROGRAM "ERPBase" "1\.0"$/)
-    expect(lines[3]).toMatch(/^#GEN \d{8}$/)
-    expect(lines[4]).toBe('#ORGNR 556677-8899')
-    expect(lines[5]).toBe('#FNAMN "Test AB"')
-    expect(lines[6]).toBe('#RAR 0 20240101 20241231')
-    expect(output).not.toContain('#FORMAT PC8')
+    expect(lines[1]).toBe('#FORMAT PC8')
+    expect(lines[2]).toBe('#SIETYP 4')
+    expect(lines[3]).toMatch(/^#PROGRAM "ERPBase" "1\.0"$/)
+    expect(lines[4]).toMatch(/^#GEN \d{8}$/)
+    expect(lines[5]).toBe('#ORGNR 556677-8899')
+    expect(lines[6]).toBe('#FNAMN "Test AB"')
+    expect(lines[7]).toBe('#RAR 0 20240101 20241231')
+  })
+
+  it('hyphenates a bare 10-digit org_number in #ORGNR', async () => {
+    results = [
+      { data: { id: 'period-1', period_start: '2024-01-01', period_end: '2024-12-31' }, error: null },
+      { data: null, error: null }, // prevPeriod
+      { data: [], error: null }, // accounts
+      { data: [], error: null }, // journal_entries (no entries -> line fetch skipped)
+      { data: [], error: null }, // dimensions
+      { data: [], error: null }, // dimension_values
+      { data: [], error: null }, // opening balances RPC
+    ]
+
+    const output = await generateSIEExport(supabase, 'company-1', {
+      ...baseOptions,
+      org_number: '5566778899',
+    })
+
+    expect(output).toContain('#ORGNR 556677-8899')
   })
 
   it('omits #ORGNR when org_number is null', async () => {