feat(astrolabe): add 3D PCA visualization for semantic search

- Add Plotly.js 3D scatter plot showing search results in PCA space
- Create shared visualization.py module to avoid code duplication
- Pass include_pca parameter through API chain to enable coordinates
- Fix OAuth redirects to use /settings/user/astroglobe

The visualization shows document embeddings projected to 3D via PCA,
with the query point highlighted in red. Uses Viridis colorscale
for score visualization, matching the existing vector-viz page.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

third_party/astroglobe/package-lock.json

@@ -13,6 +13,7 @@
         "@nextcloud/l10n": "^3.1.0",
         "@nextcloud/router": "^3.0.1",
         "@nextcloud/vue": "^8.29.2",
+        "plotly.js-dist-min": "^2.35.3",
         "vue": "^2.7.16",
         "vue-material-design-icons": "^5.3.1"
       },
@@ -9969,6 +9970,12 @@
         "pathe": "^2.0.3"
       }
     },
+    "node_modules/plotly.js-dist-min": {
+      "version": "2.35.3",
+      "resolved": "https://registry.npmjs.org/plotly.js-dist-min/-/plotly.js-dist-min-2.35.3.tgz",
+      "integrity": "sha512-sz2HLP8gkysLx/BanM2PtJTtZ1PLPwdHwMWNri2YxLBy3IOeuDsVQtlmWa4hoK3j/fi4naaD3uZJqH5ozM3zGg==",
+      "license": "MIT"
+    },
     "node_modules/possible-typed-array-names": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/possible-typed-array-names/-/possible-typed-array-names-1.1.0.tgz",