Add passwd command, fix template rendering, update deployment docs

- Add `passwd` CLI command to reset user passwords
- Fix web UI templates: parse each page template with layout so blocks
  render correctly (was outputting empty pages)
- Add login error logging for debugging auth failures
- Update README with deploy workflow and container management commands
- Update RUNBOOK for Docker-on-deimos deployment (replaces systemd refs)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/eng-pad-server/passwd.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"git.wntrmute.dev/kyle/eng-pad-server/internal/auth"
+	"git.wntrmute.dev/kyle/eng-pad-server/internal/config"
+	"git.wntrmute.dev/kyle/eng-pad-server/internal/db"
+	"github.com/spf13/cobra"
+	"golang.org/x/term"
+)
+
+var passwdCmd = &cobra.Command{
+	Use:   "passwd <username>",
+	Short: "Set password for a user",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runPasswd,
+}
+
+func init() {
+	rootCmd.AddCommand(passwdCmd)
+}
+
+func runPasswd(cmd *cobra.Command, args []string) error {
+	username := args[0]
+
+	cfg, err := config.Load(cfgFile)
+	if err != nil {
+		return err
+	}
+
+	database, err := db.Open(cfg.Database.Path)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = database.Close() }()
+
+	// Verify user exists.
+	var userID int64
+	err = database.QueryRow("SELECT id FROM users WHERE username = ?", username).Scan(&userID)
+	if err != nil {
+		return fmt.Errorf("user %q not found", username)
+	}
+
+	fmt.Print("New password: ")
+	passBytes, err := term.ReadPassword(int(os.Stdin.Fd()))
+	fmt.Println()
+	if err != nil {
+		return fmt.Errorf("read password: %w", err)
+	}
+
+	password := strings.TrimSpace(string(passBytes))
+	if password == "" {
+		return fmt.Errorf("password cannot be empty")
+	}
+
+	params := auth.Argon2Params{
+		Memory:  cfg.Auth.Argon2Memory,
+		Time:    cfg.Auth.Argon2Time,
+		Threads: cfg.Auth.Argon2Threads,
+	}
+
+	hash, err := auth.HashPassword(password, params)
+	if err != nil {
+		return fmt.Errorf("hash password: %w", err)
+	}
+
+	_, err = database.Exec("UPDATE users SET password_hash = ?, updated_at = unixepoch() WHERE id = ?", hash, userID)
+	if err != nil {
+		return fmt.Errorf("update password: %w", err)
+	}
+
+	fmt.Printf("Password updated for %q.\n", username)
+	return nil
+}