Add Servers & Tasks module ported from Schedule Task Manager

Ports cron/systemd task tracking across Debian/Raspbian servers, including
the Linux push agent (install/report/uninstall scripts, rebranded from
"schedule-task-manager-agent" to "homelab-manager-agent") and the
manual-task-entry flow for things an agent can't see (Docker jobs, backups).
The schema (servers/scheduled_tasks tables) was already in place from the
foundation pass, so this is mostly a straight port of the original's
services/routes.

Deliberate change from the original: server/token management (which mints
agent credentials) is now admin-only rather than open to any logged-in user,
and manual task CRUD is gated to operator+ — consistent with how Secrets,
IPAM, and DNS already split "configure credentials" from "everyday edits"
across roles. All mutations are audit-logged.

- server/src/services/tokens.ts, taskSync.ts: ported near-verbatim (agent
  token hashing, the agent-sync-marks-missing-as-stale-not-deleted logic).
- server/src/routes/servers.ts, tasks.ts, agentReport.ts: same contract as
  the original (agent auth is a per-server bearer token, independent of the
  session-based requireAuth used everywhere else).
- web: a single Servers & Tasks page (filter bar, task table grouped by
  server/schedule type, manual task form, and an admin-only server
  management panel with token reveal + copyable install/uninstall commands),
  replacing the original's two separate pages/apps.

Verified: full build passes; a scripted HTTP test against a running server
covers unauthenticated access, role gating at each tier (admin-only server
mgmt, operator+ task mgmt), agent bearer-token auth (valid/invalid/rotated),
manual-vs-agent task edit protection, stale-marking on re-sync, and cascade
delete — 22/22 checks passing. Real agent installation on an actual
Debian/Raspbian host still needs to be tried on the user's network.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

agent/linux/uninstall.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+# Removes the Homelab Manager task-reporting agent from this server: stops
+# and deletes its systemd timer/service, the installed script, and its
+# credentials file.
+#
+# Usage (must run as root — if not already root, put sudo right after the
+# pipe so it applies to bash, not to curl):
+#   curl -fsSL https://homelab.example.lan/agent/linux/uninstall.sh | sudo bash
+#
+set -euo pipefail
+
+INSTALL_DIR="/usr/local/bin"
+CONFIG_DIR="/etc"
+SYSTEMD_DIR="/etc/systemd/system"
+
+if [[ "$EUID" -ne 0 ]]; then
+  echo "This uninstaller must be run as root." >&2
+  echo "If you're piping from curl, put sudo right after the pipe so it elevates bash, not curl:" >&2
+  echo "  curl -fsSL ... | sudo bash" >&2
+  exit 1
+fi
+
+echo "Removing Homelab Manager agent..."
+
+if command -v systemctl >/dev/null 2>&1; then
+  systemctl disable --now homelab-manager-agent.timer >/dev/null 2>&1 || true
+fi
+
+rm -f \
+  "$SYSTEMD_DIR/homelab-manager-agent.timer" \
+  "$SYSTEMD_DIR/homelab-manager-agent.service" \
+  "$CONFIG_DIR/homelab-manager-agent.env" \
+  "$INSTALL_DIR/homelab-manager-agent.sh" \
+  /tmp/hlm-agent-response.json
+
+if command -v systemctl >/dev/null 2>&1; then
+  systemctl daemon-reload
+fi
+
+echo "Done. The agent no longer runs or reports from this server."
+echo "Its entry (and task history) in Homelab Manager is untouched —" \
+     "delete it from the Servers & Tasks page if you no longer want it tracked."