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>

package-lock.json

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       "license": "MIT"
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+      "resolved": "https://registry.npmjs.org/cron-parser/-/cron-parser-5.10.1.tgz",
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+      "license": "MIT",
+      "dependencies": {
+        "luxon": "^3.7.2"
+      },
+      "engines": {
+        "node": ">=18"
+      }
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+    "node_modules/cronstrue": {
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+      "resolved": "https://registry.npmjs.org/cronstrue/-/cronstrue-2.59.0.tgz",
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+      "license": "MIT",
+      "bin": {
+        "cronstrue": "bin/cli.js"
+      }
+    },
     "node_modules/csstype": {
       "version": "3.2.3",
       "resolved": "https://registry.npmjs.org/csstype/-/csstype-3.2.3.tgz",
@@ -3203,6 +3224,15 @@
         "yallist": "^3.0.2"
       }
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+    "node_modules/luxon": {
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     "node_modules/math-intrinsics": {
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@@ -4803,6 +4833,8 @@
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+        "cronstrue": "^2.53.0",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
         "react-router-dom": "^7.1.1"