Eliminate Python dependency: embed frontend assets in odoo-go

- Copy all OWL frontend assets (JS/CSS/XML/fonts/images) into frontend/
  directory (2925 files, 43MB) — no more runtime reads from Python Odoo
- Replace OdooAddonsPath config with FrontendDir pointing to local frontend/
- Rewire bundle.go, static.go, templates.go, webclient.go to read from
  frontend/ instead of external Python Odoo addons directory
- Auto-detect frontend/ and build/ dirs relative to binary in main.go
- Delete obsolete Python helper scripts (tools/*.py)

The Go server is now fully self-contained: single binary + frontend/ folder.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/web/static/lib/bootstrap/scss/helpers/_stacks.scss

@@ -0,0 +1,15 @@
+// scss-docs-start stacks
+.hstack {
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  align-self: stretch;
+}
+
+.vstack {
+  display: flex;
+  flex: 1 1 auto;
+  flex-direction: column;
+  align-self: stretch;
+}
+// scss-docs-end stacks