feat: git servers own credentials, one-line project adds with auto-clone, and scheduled agents

Git servers (forge_hosts) become full credential owners:
- an encrypted forge token (Fernet, HANDLER_SECRET_KEY) stored per server and
  never returned by the API (has_token flag only); used automatically by every
  project on that host and addressable as db:host:<hostname> — the reserved
  db: credential scheme is now live
- a per-server ed25519 SSH deploy key: generated server-side, public half
  shown in the dashboard to paste into the forge, private half encrypted at
  rest and materialized 0600 only in the control container (GIT_SSH_COMMAND /
  core.sshCommand)

Project registration gets a git-server mode: pick a registered server, type
owner/name, and the API derives the remote (ssh when the server has a deploy
key, https otherwise), computes root_dir under PROJECTS_ROOT, and enqueues a
new 'sync' command the worker executes (clone, or ff-only pull). Spawn always
pulls first, so runs start from the remote's latest state; POST /projects/:p/sync
and 'handler sync' re-pull on demand.

Schedules: recurring agent spawns (prefix, prompt, interval, role). The worker
fires due schedules as ordinary queued spawn commands with timestamped agent
names, so runs are fresh stateless agents and appear in the Activity audit
trail; missed intervals collapse into one catch-up run.

Dashboard: Git Servers pane shows the SSH public key (copy button) and takes a
write-only token; Repositories gains the server-first add form and a Pull now
button; new Schedules pane. Rebuilt static export. Also restores the missing
frontend/lib (api client + format helpers) the components import.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XY1tEhQZXHZ5wci7dLc7rM

.env.example

@@ -22,6 +22,13 @@ AUTH_TOKEN=change-me-to-a-long-random-string
 # Fully bring-your-own; the Notification hook is a no-op when unset.
 # WEBHOOK_URL=https://ntfy.sh/my-topic
 
+# Symmetric key for the encrypted secret store: git-server tokens and SSH private keys
+# are Fernet-encrypted with it before they reach the database. Set the SAME value on the
+# API (encrypts on write) and the control container (decrypts at clone/spawn). Generate:
+#   python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
+# Unset => storing tokens/SSH keys on git servers is refused with a clear error.
+# HANDLER_SECRET_KEY=
+
 # Base directory under which per-project roots and agent worktrees live (isolation).
 PROJECTS_ROOT=/var/lib/handler/projects