Backend improvements: views, fields_get, session, RPC stubs

- Improved auto-generated list/form/search views with priority fields,
  two-column form layout, statusbar widget, notebook for O2M fields
- Enhanced fields_get with currency_field, compute, related metadata
- Fixed session handling: handleSessionInfo/handleSessionCheck use real
  session from cookie instead of hardcoded values
- Added read_progress_bar and activity_format RPC stubs
- Improved bootstrap translations with lang_parameters
- Added "contacts" to session modules list

Server starts successfully: 14 modules, 93 models, 378 XML templates,
503 JS modules transpiled — all from local frontend/ directory.

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

addons/l10n_de/din5008.go

@@ -0,0 +1,42 @@
+package l10n_de
+
+import "fmt"
+
+// DIN5008Config holds the German business letter format configuration.
+type DIN5008Config struct {
+	// Type A: 27mm top margin, Type B: 45mm top margin
+	Type          string // "A" or "B"
+	PaperFormat   string // "A4"
+	MarginTop     int    // mm
+	MarginBottom  int    // mm
+	MarginLeft    int    // mm
+	MarginRight   int    // mm
+	AddressFieldY int    // mm from top (Type A: 27mm, Type B: 45mm)
+	InfoBlockX    int    // mm from left for info block
+}
+
+// DefaultDIN5008A returns Type A configuration.
+func DefaultDIN5008A() DIN5008Config {
+	return DIN5008Config{
+		Type: "A", PaperFormat: "A4",
+		MarginTop: 27, MarginBottom: 20,
+		MarginLeft: 25, MarginRight: 20,
+		AddressFieldY: 27, InfoBlockX: 125,
+	}
+}
+
+// DATEVExportConfig holds configuration for DATEV accounting export.
+type DATEVExportConfig struct {
+	ConsultantNumber int    // Beraternummer
+	ClientNumber     int    // Mandantennummer
+	FiscalYearStart  string // YYYY-MM-DD
+	ChartOfAccounts  string // "skr03" or "skr04"
+	BookingType      string // "DTVF" (Datev-Format)
+}
+
+// FormatDATEVHeader generates the DATEV CSV header line.
+func FormatDATEVHeader(cfg DATEVExportConfig) string {
+	return "\"EXTF\";700;21;\"Buchungsstapel\";7;;" +
+		fmt.Sprintf("%d;%d;", cfg.ConsultantNumber, cfg.ClientNumber) +
+		cfg.FiscalYearStart + ";" + "4" + ";;" // 4 = length of fiscal year
+}