Trim the Servers page down to a server list + add-server flow

Scheduled-task browsing/editing already lives on each server's detail
page (ServerDetail.tsx), so the overview page's filters, task-group
listing, and add/edit-task form were pure duplication -- the only
things it needs to do are list servers (as clickable cards) and let
an admin register new ones / issue or rotate agent tokens.

Renamed ServersTasks.tsx -> Servers.tsx to match its new, narrower
scope; updated the nav label, route, and ServerDetail's back-link
text from "Servers & Tasks" to "Servers" accordingly. No server-side
or API changes -- this only removes now-redundant frontend code.

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

README.md

@@ -26,14 +26,16 @@ All modules from the original plan are built:
 - **DNS** — zone/record management across Cloudflare, Loopia, Pi-hole, Azure
   DNS, cPanel, and Technitium; providers are configured in-app (not via env
   vars) and their credentials are encrypted at rest
-- **Servers & Tasks** — cron/systemd tracking across Debian/Raspbian servers
-  via a lightweight push agent (`agent/linux/`), plus manual entries for
-  things an agent can't see (Docker jobs, backups). A clickable server
-  overview opens a detail page with CPU/RAM/disk status, IP addresses, and
-  matching DNS names (looked up from the DNS module's cache) — live from
-  Proxmox for VM/LXC-backed servers, or from the agent's own hardware
-  report for everything else. Proxmox-linked servers also get
-  start/stop/restart buttons right on the detail page.
+- **Servers** — cron/systemd tracking across Debian/Raspbian servers via a
+  lightweight push agent (`agent/linux/`), plus manual entries for things an
+  agent can't see (Docker jobs, backups). The Servers page itself just lists
+  registered servers and (admin-only) adds new ones / issues agent tokens;
+  clicking a server opens its detail page with CPU/RAM/disk status, IP
+  addresses, matching DNS names (looked up from the DNS module's cache), and
+  its scheduled tasks — live hardware from Proxmox for VM/LXC-backed
+  servers, or from the agent's own hardware report for everything else.
+  Proxmox-linked servers also get start/stop/restart buttons right on the
+  detail page.
 - **Tailscale**, **Proxmox**, **Synology**, **Semaphore**, **Gitea**,
   and **Docker** each get their own top-level page (backed by the
   matching integration) instead of living inside a shared Integrations