refactor: move pkg/ to internal/ and update imports

Restructure project by relocating package contents from pkg/ to internal/ to better reflect internal-only usage. This commit is initial step to prepare project for public api

internal/manager/common_rpm.go

@@ -0,0 +1,72 @@
+// ALR - Any Linux Repository
+// Copyright (C) 2025 The ALR Authors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package manager
+
+import (
+	"bufio"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+type CommonRPM struct{}
+
+func (c *CommonRPM) ListInstalled(opts *Opts) (map[string]string, error) {
+	out := map[string]string{}
+	cmd := exec.Command("rpm", "-qa", "--queryformat", "%{NAME}\u200b%|EPOCH?{%{EPOCH}:}:{}|%{VERSION}-%{RELEASE}\\n")
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		return nil, err
+	}
+
+	scanner := bufio.NewScanner(stdout)
+	for scanner.Scan() {
+		name, version, ok := strings.Cut(scanner.Text(), "\u200b")
+		if !ok {
+			continue
+		}
+		version = strings.TrimPrefix(version, "0:")
+		out[name] = version
+	}
+
+	err = scanner.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	return out, nil
+}
+
+func (a *CommonRPM) IsInstalled(pkg string) (bool, error) {
+	cmd := exec.Command("rpm", "-q", "--whatprovides", pkg)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			if exitErr.ExitCode() == 1 {
+				return false, nil
+			}
+		}
+		return false, fmt.Errorf("rpm: isinstalled: %w, output: %s", err, output)
+	}
+	return true, nil
+}