Adds Codeberg as a source

pkg/appview/readme/source.go

···
 type Platform string
 
 const (
-	PlatformGitHub  Platform = "github"
-	PlatformGitLab  Platform = "gitlab"
-	PlatformTangled Platform = "tangled"
+	PlatformGitHub   Platform = "github"
+	PlatformGitLab   Platform = "gitlab"
+	PlatformTangled  Platform = "tangled"
+	PlatformCodeberg Platform = "codeberg"
 )
 
 // ParseSourceURL extracts platform, user, and repo from a source repository URL.
···
 
 	host := strings.ToLower(parsed.Host)
 
-	switch {
-	case host == "github.com":
+	switch host {
+	case "github.com":
 		// GitHub: github.com/{user}/{repo}
 		parts := strings.SplitN(path, "/", 3)
 		if len(parts) < 2 || parts[0] == "" || parts[1] == "" {
···
 		}
 		return PlatformGitHub, parts[0], parts[1], true
 
-	case host == "gitlab.com":
+	case "gitlab.com":
 		// GitLab: gitlab.com/{user}/{repo} or gitlab.com/{group}/{subgroup}/{repo}
 		// For nested groups, user = everything except last part, repo = last part
 		lastSlash := strings.LastIndex(path, "/")
···
 		}
 		return PlatformGitLab, user, repo, true
 
-	case host == "tangled.org" || host == "tangled.sh":
+	case "tangled.org", "tangled.sh":
 		// Tangled: tangled.org/{user}/{repo} or tangled.sh/@{user}/{repo} (legacy)
 		// Strip leading @ from user if present
 		path = strings.TrimPrefix(path, "@")
···
 			return "", "", "", false
 		}
 		return PlatformTangled, parts[0], parts[1], true
+
+	case "codeberg.org":
+		// Codeberg: codeberg.org/{user}/{repo}
+		parts := strings.SplitN(path, "/", 3)
+		if len(parts) < 2 || parts[0] == "" || parts[1] == "" {
+			return "", "", "", false
+		}
+		return PlatformCodeberg, parts[0], parts[1], true
 
 	default:
 		return "", "", "", false
···
 	case PlatformTangled:
 		// https://tangled.org/{user}/{repo}/raw/{branch}/README.md
 		return fmt.Sprintf("https://tangled.org/%s/%s/raw/%s/README.md", user, repo, branch)
+
+	case PlatformCodeberg:
+		// https://codeberg.org/{user}/{repo}/raw/branch/{branch}/README.md
+		return fmt.Sprintf("https://codeberg.org/%s/%s/raw/branch/%s/README.md", user, repo, branch)
 
 	default:
 		return ""

pkg/appview/readme/source_test.go

···
 			wantOK:       true,
 		},
 
+		// Codeberg
+		{
+			name:         "codeberg standard",
+			sourceURL:    "https://codeberg.org/user/repo",
+			wantPlatform: PlatformCodeberg,
+			wantUser:     "user",
+			wantRepo:     "repo",
+			wantOK:       true,
+		},
+
 		// Unsupported / Invalid
 		{
 			name:      "unsupported platform",
···
 			sourceURL: "https://tangled.org/@user/repo",
 			branch:    "main",
 			want:      "https://tangled.org/user/repo/raw/main/README.md",
+		},
+
+		// Codeberg
+		{
+			name:      "codeberg main",
+			sourceURL: "https://codeberg.org/user/repo",
+			branch:    "main",
+			want:      "https://codeberg.org/user/repo/raw/branch/main/README.md",
 		},
 
 		// Unsupported