fix: bust stale Dagger cache and harden SSH key normalisation in Deployer (#406)

## Summary

Fixes the persistent `Load key "/root/.ssh/id_ed25519": error in libcrypto` failures in the `deploy-apk` and `deploy-linux` CI jobs (and the `website` workflow SSH steps) that have been occurring on every deploy run since the jobs first started running after #369.

Closes #404

### Root cause (diagnosed from run #1516 log)

Two compounding problems were found:

1. **Stale Dagger cache** — The `tr -d \x27\r\x27` normalisation step added in #369 was shown as `CACHED` by Dagger on every subsequent run. Dagger caches by input-content hash; if the very first execution produced a corrupted key file, that broken cached layer is replayed forever.

2. **`.ssh/` directory permissions** — Dagger creates parent directories for secret mounts with 755 permissions. Mounting the raw key directly inside `/root/.ssh/` may cause Dagger to (re-)create that directory with 755 instead of the 700 that OpenSSH requires.

### Changes (`ci/main.go` — `Deployer` function only)

- **Explicit `.ssh` setup**: `mkdir -p /root/.ssh && chmod 700 /root/.ssh` runs before any Dagger secret mount.
- **Move raw-key mount out of `.ssh/`**: Secret mounted at `/tmp/id_ed25519.raw`.
- **Python3 normalisation instead of `tr`**: Handles CRLF, bare-CR, and missing trailing newline. Changing the command changes the Dagger cache key, forcing a fresh read of the current live secret.

## Test plan

- [ ] `deploy-apk` job completes without `error in libcrypto`
- [ ] `deploy-linux` job completes without `error in libcrypto`
- [ ] `publish-android` (Play Store) job continues to succeed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/406

ci/main.go

@@ -338,12 +338,17 @@ func (m *Ci) Deployer(sshKey *dagger.Secret, knownHosts *dagger.Secret) *dagger.
 	return dag.Container().
 		From("alpine:3.21").
 		WithExec([]string{"apk", "--no-cache", "add", "rsync", "openssh-client", "python3", "tar"}).
-		// Mount at a raw path so we can normalise before use: strip any CRLF line
-		// endings that appear when the key is stored or exported on Windows, which
-		// cause "error in libcrypto" in Alpine's LibreSSL-backed openssh.
-		WithMountedSecret("/root/.ssh/id_ed25519.raw", sshKey, dagger.ContainerWithMountedSecretOpts{Mode: 0600}).
-		WithExec([]string{"sh", "-c",
-			"tr -d '\\r' < /root/.ssh/id_ed25519.raw > /root/.ssh/id_ed25519 && chmod 600 /root/.ssh/id_ed25519"}).
+		// Create .ssh with strict permissions before Dagger mounts anything there,
+		// so the directory is 700 (not Dagger's default 755).
+		WithExec([]string{"sh", "-c", "mkdir -p /root/.ssh && chmod 700 /root/.ssh"}).
+		// Mount the raw key outside .ssh so Dagger cannot override the directory
+		// permissions we just set above.
+		WithMountedSecret("/tmp/id_ed25519.raw", sshKey, dagger.ContainerWithMountedSecretOpts{Mode: 0600}).
+		// Normalise with Python3: strip CRLF/bare-CR, ensure trailing newline.
+		// Using Python3 (not tr) changes the Dagger cache key so stale cached
+		// results from the old tr-based step are not reused.
+		WithExec([]string{"python3", "-c",
+			"import os; raw=open('/tmp/id_ed25519.raw','rb').read(); key=raw.replace(b'\\r\\n',b'\\n').replace(b'\\r',b'\\n'); key=key if key.endswith(b'\\n') else key+b'\\n'; open('/root/.ssh/id_ed25519','wb').write(key); os.chmod('/root/.ssh/id_ed25519',0o600)"}).
 		WithMountedSecret("/root/.ssh/known_hosts", knownHosts, dagger.ContainerWithMountedSecretOpts{Mode: 0644}).
 		WithEnvVariable("RSYNC_RSH", "ssh -i /root/.ssh/id_ed25519")
 }