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/_placeholders.scss

@@ -0,0 +1,51 @@
+.placeholder {
+  display: inline-block;
+  min-height: 1em;
+  vertical-align: middle;
+  cursor: wait;
+  background-color: currentcolor;
+  opacity: $placeholder-opacity-max;
+
+  &.btn::before {
+    display: inline-block;
+    content: "";
+  }
+}
+
+// Sizing
+.placeholder-xs {
+  min-height: .6em;
+}
+
+.placeholder-sm {
+  min-height: .8em;
+}
+
+.placeholder-lg {
+  min-height: 1.2em;
+}
+
+// Animation
+.placeholder-glow {
+  .placeholder {
+    animation: placeholder-glow 2s ease-in-out infinite;
+  }
+}
+
+@keyframes placeholder-glow {
+  50% {
+    opacity: $placeholder-opacity-min;
+  }
+}
+
+.placeholder-wave {
+  mask-image: linear-gradient(130deg, $black 55%, rgba(0, 0, 0, (1 - $placeholder-opacity-min)) 75%, $black 95%);
+  mask-size: 200% 100%;
+  animation: placeholder-wave 2s linear infinite;
+}
+
+@keyframes placeholder-wave {
+  100% {
+    mask-position: -200% 0%;
+  }
+}