Refactor: migrate pdf_parser.py to golang (#16323)

### What problem does this PR solve?

Http API based on onnx model.
pdf_parser.py to golang

### Type of change

- [x] Refactoring

internal/deepdoc/parser/pdf/pdfoxide/cropbox_test.go

@@ -0,0 +1,128 @@
+package pdfoxide
+
+import (
+	"math"
+	"testing"
+)
+
+func TestParseCropBoxFromRaw(t *testing.T) {
+	eps := 1e-6
+
+	tests := []struct {
+		name    string
+		raw     string
+		pageIdx int
+		want    [4]float64
+		ok      bool
+	}{
+		{
+			name: "standard A4 portrait",
+			raw:  "/CropBox [0 0 595.28 841.89]",
+			want: [4]float64{0, 0, 595.28, 841.89},
+			ok:   true,
+		},
+		{
+			name: "non-zero origin",
+			raw:  "/CropBox [30 20 575 832]",
+			want: [4]float64{30, 20, 575, 832},
+			ok:   true,
+		},
+		{
+			name: "with extra whitespace",
+			raw:  "/CropBox  [  0.5   10.25   595.3   842.0  ]",
+			want: [4]float64{0.5, 10.25, 595.3, 842.0},
+			ok:   true,
+		},
+		{
+			name: "no spaces inside brackets",
+			raw:  "/CropBox[0 0 595 842]",
+			want: [4]float64{0, 0, 595, 842},
+			ok:   true,
+		},
+		{
+			name:    "page index 1 picks second CropBox",
+			raw:     "/CropBox [0 0 1 1] /Rotate 90 /CropBox [2 2 3 3]",
+			pageIdx: 1,
+			want:    [4]float64{2, 2, 3, 3},
+			ok:      true,
+		},
+		{
+			name:    "page index out of range",
+			raw:     "/CropBox [0 0 1 1]",
+			pageIdx: 5,
+			want:    [4]float64{},
+			ok:      false,
+		},
+		{
+			name: "no cropbox",
+			raw:  "/MediaBox [0 0 595 842] /Rotate 90",
+			want: [4]float64{},
+			ok:   false,
+		},
+		{
+			name: "empty input",
+			raw:  "",
+			want: [4]float64{},
+			ok:   false,
+		},
+		{
+			name: "incomplete array — fewer than 4 values",
+			raw:  "/CropBox [0 0 595]",
+			want: [4]float64{},
+			ok:   false,
+		},
+		{
+			name: "negative values",
+			raw:  "/CropBox [-10 -20 595 842]",
+			want: [4]float64{-10, -20, 595, 842},
+			ok:   true,
+		},
+		{
+			name: "real pypdf output format (multiple spaces, decimals)",
+			raw:  "/Type /Page /MediaBox [0 0 595.2756 841.8898] /CropBox [30.0 20.0 575.0 832.0] /Rotate 90",
+			want: [4]float64{30.0, 20.0, 575.0, 832.0},
+			ok:   true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := parseCropBoxFromRaw([]byte(tt.raw), tt.pageIdx)
+			if ok != tt.ok {
+				t.Fatalf("ok=%v want %v", ok, tt.ok)
+			}
+			if !ok {
+				return
+			}
+			for i := 0; i < 4; i++ {
+				if math.Abs(got[i]-tt.want[i]) > eps {
+					t.Errorf("[%d]: got %.4f, want %.4f", i, got[i], tt.want[i])
+				}
+			}
+		})
+	}
+}
+
+func TestParseFloat(t *testing.T) {
+	tests := []struct {
+		s    string
+		want float64
+		n    int
+	}{
+		{"0", 0, 1},
+		{"595.28", 595.28, 6},
+		{"  42", 42, 4},
+		{"-10.5", -10.5, 5},
+		{"+3.14", 3.14, 5},
+		{"123abc", 123, 3},
+		{"abc", 0, 0},
+		{"", 0, 0},
+		{".5", 0.5, 2},
+	}
+	for _, tt := range tests {
+		v, n := parseFloat([]byte(tt.s))
+		if n != tt.n || math.Abs(v-tt.want) > 1e-6 {
+			t.Errorf("parseFloat(%q) = (%.4f, %d), want (%.4f, %d)",
+				tt.s, v, n, tt.want, tt.n)
+		}
+	}
+}