Add a "Sync from Tailscale" action to IP Addresses (IPAM)

IPAM was entirely manual — Tailscale device IPs never showed up there
even though the Tailscale integration already lists them. Add an
explicit sync action (matching this app's existing pattern of
user-triggered syncs rather than silent background polling).

- New source column on ipam_entries (null = manual, "tailscale" =
  auto-synced) so a re-sync only ever touches rows it created itself —
  a manually-entered IP that happens to collide with a tailnet address
  is left untouched and reported back as skipped, never overwritten.
- POST /api/ipam/sync-tailscale pulls every enabled Tailscale
  integration's device list, upserting by primary IP (label, OS in
  notes, vendor "Tailscale"); one unreachable Tailscale integration
  doesn't block others.
- New "Sync from Tailscale" button on the IP Addresses page, with a
  small "synced" badge marking which rows came from it.

Also fixed a longstanding TODO found in the same file: the "DNS
records" column always showed "-" because matchingDnsRecords was
hardcoded to an empty array from before the DNS module existed. It
now does the same content-based reverse lookup against the DNS
module's record cache used elsewhere in the app.

Verified end-to-end by running the real server with Tailscale's fetch
call intercepted at the process level (its adapter hardcodes
api.tailscale.com with no configurable URL, so it can't be pointed at
a mock server the way Proxmox/Synology can): confirmed add, the
manual-entry skip/never-overwrite behavior, idempotent re-sync
(add -> update), and the DNS-matching fix, all against the real
route and adapter code.

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

server/src/db/schema.ts

@@ -74,6 +74,7 @@ export const ipamEntries = sqliteTable("ipam_entries", {
   vendor: text("vendor"),
   location: text("location"),
   notes: text("notes"),
+  source: text("source"), // null = entered manually; "tailscale" = auto-synced from a Tailscale integration
   createdAt: text("created_at")
     .notNull()
     .default(sql`(current_timestamp)`),