feat(docs): mkdocs-style documentation site served at /docs

Full documentation hub replacing the release-notes-only view:
- Handbook pages (docs/handbook) for all features and admin/betrieb
- API reference generated from lib/api-spec/openapi.yaml via
  scripts/src/generate-docs.mjs (replaces sync-release-docs.mjs):
  endpoints, schemas/fields, search index, per-release snapshots
- mkdocs layout: sidebar nav, right TOC with scrollspy, search overlay,
  version dropdown, repo link
- FieldHelp (?) buttons in forms linking to reference field docs
- v0.7.0 release notes backfilled, v0.8.0 release notes added

pnpm-lock.yaml

@@ -78,6 +78,9 @@ catalogs:
     wouter:
       specifier: 3.10.0
       version: 3.10.0
+    yaml:
+      specifier: 2.9.0
+      version: 2.9.0
     zod:
       specifier: 4.4.3
       version: 4.4.3
@@ -718,6 +721,9 @@ importers:
       tsx:
         specifier: 'catalog:'
         version: 4.23.4
+      yaml:
+        specifier: 'catalog:'
+        version: 2.9.0
 
 packages:
 
@@ -3751,6 +3757,11 @@ packages:
     engines: {node: '>= 14.6'}
     hasBin: true
 
+  yaml@2.9.0:
+    resolution: {integrity: sha512-2AvhNX3mb8zd6Zy7INTtSpl1F15HW6Wnqj0srWlkKLcpYl/gMIMJiyuGq2KeI2YFxUPjdlB+3Lc10seMLtL4cA==}
+    engines: {node: '>= 14.6'}
+    hasBin: true
+
   yocto-queue@1.2.2:
     resolution: {integrity: sha512-4LCcse/U2MHZ63HAJVE+v71o7yOdIe4cZ70Wpf8D/IyjDKYQLV5GD46B+hSTjJsvV5PztjvHoU580EftxjDZFQ==}
     engines: {node: '>=12.20'}
@@ -6596,6 +6607,8 @@ snapshots:
 
   yaml@2.8.4: {}
 
+  yaml@2.9.0: {}
+
   yocto-queue@1.2.2: {}
 
   yoctocolors@2.1.2: {}