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>

types/index.ts

@@ -2141,8 +2141,6 @@ export interface SIEExportOptions {
    * our closing entry would zero out the P&L accounts.
    */
   exclude_year_end_closing?: boolean
-  /** Emit #FORMAT PC8 in the header. Set true when the caller will encode the output as CP437. */
-  emit_format_pc8?: boolean
 }
 
 // Input types for creating entries