feat(fleet): export a whole-fleet Markdown dossier (#1334)

* feat(fleet): export a whole-fleet Markdown dossier

Add an admin-only "Export Dossier" action to the Fleet view that walks
every node and stack, pairs each stack's generated Compose anatomy with
its operator notes, and downloads a folder-structured homelab-dossier.zip
(index, per-node and per-stack pages, plus fleet-wide port, volume,
network, env, access-URL, and VLAN/firewall maps).

Reuses the existing stack dossier and anatomy Markdown generators by
extracting the shared Compose parsers into a frontend lib module.
Unreachable nodes are recorded with a reason and never block the export;
only env variable names and counts are ever emitted, never values.

* fix(fleet): unique stack slugs and reproducible dossier archive

Disambiguate stack names on one node that slugify to the same value (e.g.
`Web` and `web` on a case-sensitive host) with a per-node slug map shared by
the node-page links and the file emission, so neither overwrites the other.
Pin a fixed entry timestamp on the zip so the archive bytes are a pure
function of the file map rather than the wall clock.

frontend/package-lock.json

@@ -36,6 +36,7 @@
         "cmdk": "^1.1.1",
         "cronstrue": "^3.14.0",
         "date-fns": "^4.3.0",
+        "fflate": "^0.8.2",
         "geist": "^1.7.1",
         "lucide-react": "^1.16.0",
         "monaco-editor": "^0.55.1",
@@ -5055,6 +5056,12 @@
         }
       }
     },
+    "node_modules/fflate": {
+      "version": "0.8.3",
+      "resolved": "https://registry.npmjs.org/fflate/-/fflate-0.8.3.tgz",
+      "integrity": "sha512-tbZNuJrLwGUp3zshBtdy4W+ORxZuIh8a5ilyIEQDC5rY1f3U20JMry0Ll3WBzU58EZKsEuJFXhb5gwv8CsPvgA==",
+      "license": "MIT"
+    },
     "node_modules/file-entry-cache": {
       "version": "8.0.0",
       "resolved": "https://registry.npmjs.org/file-entry-cache/-/file-entry-cache-8.0.0.tgz",