chore(release): self-hosted updater on update.netralax.cloud

Switches the Tauri updater endpoint from GitHub Releases to a static
host. New Ed25519 pubkey (old private key was lost); existing 0.10.x
installs need one manual reinstall to pick up the new updater identity.

Release flow is now pnpm release <version> <notes> which bumps,
builds + signs locally, scps artifacts to the server, commits, tags.
GitHub workflow stays as workflow_dispatch backup (Windows only).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.env.release.example

@@ -0,0 +1,21 @@
+# Copy to .env.release (gitignored) and fill in.
+# Consumed by scripts/release.mjs.
+
+# Absolute path to the private key file produced by `tauri signer generate`.
+TAURI_SIGNING_PRIVATE_KEY_PATH=C:/Users/denni/.tauri/chatapp.key
+
+# Password set when generating the key. Leave empty if none.
+TAURI_SIGNING_PRIVATE_KEY_PASSWORD=
+
+# Host serving latest.json + installer artifacts over HTTPS.
+UPDATE_HOST=update.netralax.cloud
+
+# SSH user on UPDATE_HOST with write access to UPDATE_REMOTE_PATH.
+UPDATE_SSH_USER=chatapp-deploy
+
+# Optional: path to the SSH private key. Omit to fall back on ssh-agent or the
+# default id_rsa.
+UPDATE_SSH_KEY=
+
+# Absolute path on the server where windows/ artifacts + latest.json live.
+UPDATE_REMOTE_PATH=/var/www/updates/windows