feat: implement profile summary cards with GraphQL fetch and Action wrapper

- Add GraphQL client fetching profile, stats, language aggregation, and
  per-repo commit histograms for the productive-time heatmap.
- Render real SVG cards (profile details, top languages, stats grid,
  weekday×hour heatmap) with XML escaping and thousands-formatted numbers.
- Expand theme palette to 30 built-ins ported from github-readme-stats;
  add -list-themes, multi-theme rendering, and 'all' shortcut.
- Package as Docker-based GitHub Action (action.yml, Dockerfile,
  entrypoint.sh) with optional auto-commit of generated cards.
- Release workflow publishes GHCR image and cross-platform binaries on
  v* tags.
- Unit tests cover rendering, XML escape, number formatting, language sort.

main.go

@@ -5,6 +5,8 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"strings"
+	"time"
 
 	"github.com/tiennm99/ghstats/internal/card"
 	"github.com/tiennm99/ghstats/internal/github"
@@ -13,36 +15,97 @@ import (
 
 func main() {
 	var (
-		user    = flag.String("user", "", "GitHub username (required)")
-		token   = flag.String("token", os.Getenv("GITHUB_TOKEN"), "GitHub token (or env GITHUB_TOKEN)")
-		out     = flag.String("out", "output", "output directory for SVG cards")
-		themeID = flag.String("theme", "dracula", "theme id (dracula, default, github)")
+		user       = flag.String("user", "", "GitHub username (required)")
+		token      = flag.String("token", os.Getenv("GITHUB_TOKEN"), "GitHub token (or env GITHUB_TOKEN)")
+		out        = flag.String("out", "output", "output directory")
+		themesFlag = flag.String("themes", "dracula", "comma-separated theme ids, or 'all'")
+		tzName     = flag.String("tz", "Local", "timezone for productive-time card (IANA name, e.g. Asia/Saigon)")
+		topRepos   = flag.Int("top-repos", 10, "owned repos to sample for productive-time heatmap (0 to skip)")
+		perRepo    = flag.Int("commits-per-repo", 100, "max commits sampled per repo")
+		listThemes = flag.Bool("list-themes", false, "print available theme ids and exit")
 	)
 	flag.Parse()
 
+	if *listThemes {
+		for _, id := range theme.IDs() {
+			fmt.Println(id)
+		}
+		return
+	}
+
 	if *user == "" {
 		fmt.Fprintln(os.Stderr, "error: -user is required")
 		flag.Usage()
 		os.Exit(2)
 	}
 
-	th, ok := theme.Lookup(*themeID)
-	if !ok {
-		fmt.Fprintf(os.Stderr, "error: unknown theme %q\n", *themeID)
+	selected, err := resolveThemes(*themesFlag)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(2)
 	}
 
+	loc, err := time.LoadLocation(*tzName)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "warn: unknown timezone %q, falling back to UTC\n", *tzName)
+		loc = time.UTC
+	}
+
 	client := github.NewClient(*token)
-	profile, err := client.Profile(*user)
+	profile, err := client.FetchProfile(*user)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "error: fetch profile: %v\n", err)
 		os.Exit(1)
 	}
 
-	if err := card.RenderAll(profile, th, *out); err != nil {
-		fmt.Fprintf(os.Stderr, "error: render cards: %v\n", err)
-		os.Exit(1)
+	if *topRepos > 0 && profile.ID != "" {
+		repos := profile.TopRepos
+		if len(repos) > *topRepos {
+			repos = repos[:*topRepos]
+		}
+		if err := client.FetchProductive(profile, repos, loc, *perRepo); err != nil {
+			fmt.Fprintf(os.Stderr, "warn: productive-time fetch: %v\n", err)
+		}
 	}
 
-	fmt.Printf("wrote cards to %s/%s/\n", *out, th.ID)
+	for _, t := range selected {
+		if err := card.RenderAll(profile, t, *out); err != nil {
+			fmt.Fprintf(os.Stderr, "error: render %s: %v\n", t.ID, err)
+			os.Exit(1)
+		}
+		fmt.Printf("wrote %s/%s/\n", *out, t.ID)
+	}
+}
+
+func resolveThemes(spec string) ([]theme.Theme, error) {
+	spec = strings.TrimSpace(spec)
+	if spec == "" {
+		return nil, fmt.Errorf("no themes specified")
+	}
+	if spec == "all" {
+		ids := theme.IDs()
+		out := make([]theme.Theme, 0, len(ids))
+		for _, id := range ids {
+			if t, ok := theme.Lookup(id); ok {
+				out = append(out, t)
+			}
+		}
+		return out, nil
+	}
+	var out []theme.Theme
+	for _, id := range strings.Split(spec, ",") {
+		id = strings.TrimSpace(id)
+		if id == "" {
+			continue
+		}
+		t, ok := theme.Lookup(id)
+		if !ok {
+			return nil, fmt.Errorf("unknown theme %q (use -list-themes)", id)
+		}
+		out = append(out, t)
+	}
+	if len(out) == 0 {
+		return nil, fmt.Errorf("no valid themes")
+	}
+	return out, nil
 }