docs: Major documentation structure optimization

- Reorganize docs following industry best practices (Microsoft Docs, Stripe Docs)
- Move architecture specs from community to dedicated /architecture folder
- Create essential missing docs: FAQ, Troubleshooting, Security
- Add Migration guide section
- Simplify guide structure by removing redundant files
- Update all meta.json files for better navigation
- Consolidate community section
- Improve main index page with clear navigation

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

…unity/architecture/specs/architecture.md docs/architecture/architecture.mddocs/community/architecture/specs/architecture.md renamed to docs/architecture/architecture.md docs/community/architecture/specs/architecture.md renamed to docs/architecture/architecture.md

@@ -0,0 +1,12 @@
+{
+  "title": "Architecture",
+  "pages": [
+    "architecture",
+    "project-structure",
+    "rendering-specification",
+    "component",
+    "component-library",
+    "component-package",
+    "base-components"
+  ]
+}