feat: sync with upstream — v1.2.0, in-app updates, Projects, modules

Brings the public tree back in line with the development repo after several
weeks of drift caused by a stale publish include list.

New:
- In-app update path: GET /update/check compares the checkout against
  origin/main and POST /update/apply runs `ncp upgrade` detached (pull,
  rebuild, restart). The sidebar shows the version, checks on click, and
  offers an "update available" pill.
- Projects: a project workspace groups chats and RAG documents, with
  per-project instructions and document retrieval scoped to the active
  project. Replaces the standalone Documents page.
- modules/: auto-discovered feature plugins (mail, network) with their
  frontend counterparts and tests.
- Memory curation runs in-process (synapse/memory/curator.py) on the chat
  model when a conversation goes idle. The separate memory service on :8001
  is gone, along with the launcher lines that started it.

Also: the KDE theme, panel and Promethean terminal assets, the full test
suite, and VERSION 1.2.0.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

assets/themes/KDE/look-and-feel/com.nexusos.desktop/metadata.json

@@ -0,0 +1,22 @@
+{
+    "KPlugin": {
+        "Authors": [
+            {
+                "Name": "NexusOS"
+            }
+        ],
+        "Category": "",
+        "Description": "Dark purple NexusOS desktop with lime-green accents",
+        "Id": "com.nexusos.desktop",
+        "License": "GPL",
+        "Name": "NexusOS",
+        "ServiceTypes": [
+            "Plasma/LookAndFeel"
+        ],
+        "Version": "1.0",
+        "Website": ""
+    },
+    "X-Plasma-APIVersion": "2",
+    "X-Plasma-MainScript": "defaults",
+    "KPackageStructure": "Plasma/LookAndFeel"
+}