feat(cli): implement device add with signing + deploy key

- Create crates/relicario-cli/src/device.rs: local key storage under
  ~/.config/relicario/devices/<name>/, current-device tracking, and
  git signing config (gpg.format=ssh, user.signingkey, core.sshCommand)
- Add Device command to CLI with add/revoke/list subcommands
- cmd_device add: generates two ed25519 keypairs (signing + deploy),
  registers deploy key via Gitea API, stores keys at 0600, configures
  git SSH signing, updates .relicario/devices.json and commits
- Gitea config read from flags or RELICARIO_GITEA_{URL,TOKEN,OWNER,REPO}
- --no-gitea flag skips API registration for non-Gitea remotes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/relicario-cli/src/device.rs

@@ -0,0 +1,166 @@
+//! Local device key storage and git signing configuration.
+//!
+//! Keys live under `~/.config/relicario/devices/<device-name>/`:
+//!   signing.key   — ed25519 private key (OpenSSH, 0600)
+//!   signing.pub   — ed25519 public key (OpenSSH single line)
+//!   deploy.key    — ed25519 private key for git push (OpenSSH, 0600)
+//!   deploy.pub    — ed25519 public key registered as Gitea deploy key
+//!   gitea_key_id  — numeric Gitea deploy key ID for later revocation
+//!
+//! The file `~/.config/relicario/devices/current` holds the active device name
+//! (one plain-text line).
+
+use std::fs::{self, Permissions};
+use std::path::PathBuf;
+
+use anyhow::{Context, Result};
+use zeroize::Zeroizing;
+
+/// `~/.config/relicario/devices/`
+pub fn devices_dir() -> Result<PathBuf> {
+    let config = dirs::config_dir()
+        .ok_or_else(|| anyhow::anyhow!("no config directory available"))?;
+    Ok(config.join("relicario").join("devices"))
+}
+
+/// `~/.config/relicario/devices/<name>/`
+pub fn device_dir(name: &str) -> Result<PathBuf> {
+    Ok(devices_dir()?.join(name))
+}
+
+/// Read the current device name from `devices/current`, or `None` if not set.
+pub fn current_device() -> Result<Option<String>> {
+    let path = devices_dir()?.join("current");
+    if !path.exists() {
+        return Ok(None);
+    }
+    let name = fs::read_to_string(&path)
+        .context("read current device")?
+        .trim()
+        .to_string();
+    if name.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(name))
+    }
+}
+
+/// Write the active device name to `devices/current`.
+pub fn set_current_device(name: &str) -> Result<()> {
+    let dir = devices_dir()?;
+    fs::create_dir_all(&dir).context("create devices dir")?;
+    fs::write(dir.join("current"), format!("{name}\n"))
+        .context("write current device")?;
+    Ok(())
+}
+
+/// Store all keys for a device, applying restrictive permissions on private
+/// key files on Unix.
+pub fn store_device_keys(
+    name: &str,
+    signing_private: &str,
+    signing_public: &str,
+    deploy_private: &str,
+    deploy_public: &str,
+    gitea_key_id: u64,
+) -> Result<()> {
+    let dir = device_dir(name)?;
+    fs::create_dir_all(&dir).context("create device dir")?;
+
+    fs::write(dir.join("signing.key"), signing_private)
+        .context("write signing.key")?;
+    fs::write(dir.join("signing.pub"), signing_public)
+        .context("write signing.pub")?;
+    fs::write(dir.join("deploy.key"), deploy_private)
+        .context("write deploy.key")?;
+    fs::write(dir.join("deploy.pub"), deploy_public)
+        .context("write deploy.pub")?;
+    fs::write(dir.join("gitea_key_id"), gitea_key_id.to_string())
+        .context("write gitea_key_id")?;
+
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        fs::set_permissions(dir.join("signing.key"), Permissions::from_mode(0o600))
+            .context("chmod signing.key")?;
+        fs::set_permissions(dir.join("deploy.key"), Permissions::from_mode(0o600))
+            .context("chmod deploy.key")?;
+    }
+
+    Ok(())
+}
+
+/// Load the signing private key for a device.
+pub fn load_signing_key(name: &str) -> Result<Zeroizing<String>> {
+    let path = device_dir(name)?.join("signing.key");
+    let key = fs::read_to_string(&path)
+        .with_context(|| format!("read signing key for device '{name}'"))?;
+    Ok(Zeroizing::new(key))
+}
+
+/// Load the deploy private key for a device.
+pub fn load_deploy_key(name: &str) -> Result<Zeroizing<String>> {
+    let path = device_dir(name)?.join("deploy.key");
+    let key = fs::read_to_string(&path)
+        .with_context(|| format!("read deploy key for device '{name}'"))?;
+    Ok(Zeroizing::new(key))
+}
+
+/// Load the Gitea deploy key ID for a device.
+pub fn load_gitea_key_id(name: &str) -> Result<u64> {
+    let path = device_dir(name)?.join("gitea_key_id");
+    let id_str = fs::read_to_string(&path)
+        .with_context(|| format!("read Gitea key ID for device '{name}'"))?;
+    id_str.trim().parse().context("parse Gitea key ID")
+}
+
+/// Delete the local key directory for a device.
+pub fn delete_device_keys(name: &str) -> Result<()> {
+    let dir = device_dir(name)?;
+    if dir.exists() {
+        fs::remove_dir_all(&dir)
+            .with_context(|| format!("delete device dir for '{name}'"))?;
+    }
+    Ok(())
+}
+
+/// Configure git in `vault_root` to:
+///  - sign commits with the device's signing key (SSH format)
+///  - push via SSH using the device's deploy key
+pub fn configure_git_signing(vault_root: &std::path::Path, name: &str) -> Result<()> {
+    let dir = device_dir(name)?;
+    let signing_key = dir.join("signing.key");
+    let deploy_key = dir.join("deploy.key");
+
+    // gpg.format = ssh so git uses SSH-format signing
+    crate::helpers::git_command(vault_root, &["config", "gpg.format", "ssh"])
+        .status()
+        .context("git config gpg.format")?;
+
+    // user.signingkey = path to the private key file
+    crate::helpers::git_command(
+        vault_root,
+        &["config", "user.signingkey", &signing_key.to_string_lossy()],
+    )
+    .status()
+    .context("git config user.signingkey")?;
+
+    // commit.gpgsign = true
+    crate::helpers::git_command(vault_root, &["config", "commit.gpgsign", "true"])
+        .status()
+        .context("git config commit.gpgsign")?;
+
+    // core.sshCommand — use only the deploy key for push
+    let ssh_cmd = format!(
+        "ssh -i {} -o IdentitiesOnly=yes",
+        deploy_key.display()
+    );
+    crate::helpers::git_command(
+        vault_root,
+        &["config", "core.sshCommand", &ssh_cmd],
+    )
+    .status()
+    .context("git config core.sshCommand")?;
+
+    Ok(())
+}