chore: modernize Go 1.26, update deps, fix lint issues

- Update Go version from 1.19 to 1.26
- Update all dependencies to latest versions
- Fix staticcheck warnings (unused vars, types, functions)
- Remove unused svgToPng function
- Add GitHub Actions CI workflow

graph/svg/svg.go

@@ -4,29 +4,17 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
-	"image"
-	"image/png"
-	"os"
-	"sync"
 	"time"
 
 	svg "github.com/ajstarks/svgo"
-	"github.com/srwiley/oksvg"
-	"github.com/srwiley/rasterx"
 	sc "github.com/taigrr/simplecolorpalettes/simplecolor"
 
 	"github.com/taigrr/gico/graph/common"
 )
 
-var (
-	colorsLoaded sync.Once
-	colorScheme  []sc.SimpleColor
-)
-
 func GetWeekSVG(frequencies []int, shouldHighlight bool) bytes.Buffer {
 	squareColors := []sc.SimpleColor{}
 	min, max := common.MinMax(frequencies)
-	// fmt.Println(frequencies)
 	for _, f := range frequencies {
 		squareColors = append(squareColors, common.ColorForFrequency(f, min, max))
 	}
@@ -81,36 +69,7 @@ func drawYearImage(c []sc.SimpleColor, freq []int, shouldHighlight bool) bytes.B
 		}
 		canvas.Square(2*squareLength+width/(len(c)/7+1)*(i/7)+squareLength*2, squareLength/2+height/7*(i%7), squareLength, fmt.Sprintf("fill:%s; value:%d", s.ToHex(), freq[i]))
 	}
-	// canvas.Text(2*squareLength, squareLength*3, "Mon", fmt.Sprintf("text-anchor:middle;font-size:%dpx;fill:black", squareLength))
-	// canvas.Text(2*squareLength, int(float64(squareLength)*6.5), "Wed", fmt.Sprintf("text-anchor:middle;font-size:%dpx;fill:black", squareLength))
-	// canvas.Text(2*squareLength, int(float64(squareLength))*10, "Fri", fmt.Sprintf("text-anchor:middle;font-size:%dpx;fill:black", squareLength))
 	canvas.End()
 	sbw.Flush()
 	return sb
 }
-
-func svgToPng() {
-	w, h := 512, 512
-
-	in, err := os.Open("in.svg")
-	if err != nil {
-		panic(err)
-	}
-	defer in.Close()
-
-	icon, _ := oksvg.ReadIconStream(in)
-	icon.SetTarget(0, 0, float64(w), float64(h))
-	rgba := image.NewRGBA(image.Rect(0, 0, w, h))
-	icon.Draw(rasterx.NewDasher(w, h, rasterx.NewScannerGV(w, h, rgba, rgba.Bounds())), 1)
-
-	out, err := os.Create("out.png")
-	if err != nil {
-		panic(err)
-	}
-	defer out.Close()
-
-	err = png.Encode(out, rgba)
-	if err != nil {
-		panic(err)
-	}
-}