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/mixins/_gradients.scss

@@ -0,0 +1,47 @@
+// Gradients
+
+// scss-docs-start gradient-bg-mixin
+@mixin gradient-bg($color: null) {
+  background-color: $color;
+
+  @if $enable-gradients {
+    background-image: var(--#{$prefix}gradient);
+  }
+}
+// scss-docs-end gradient-bg-mixin
+
+// scss-docs-start gradient-mixins
+// Horizontal gradient, from left to right
+//
+// Creates two color stops, start and end, by specifying a color and position for each color stop.
+@mixin gradient-x($start-color: $gray-700, $end-color: $gray-800, $start-percent: 0%, $end-percent: 100%) {
+  background-image: linear-gradient(to right, $start-color $start-percent, $end-color $end-percent);
+}
+
+// Vertical gradient, from top to bottom
+//
+// Creates two color stops, start and end, by specifying a color and position for each color stop.
+@mixin gradient-y($start-color: $gray-700, $end-color: $gray-800, $start-percent: null, $end-percent: null) {
+  background-image: linear-gradient(to bottom, $start-color $start-percent, $end-color $end-percent);
+}
+
+@mixin gradient-directional($start-color: $gray-700, $end-color: $gray-800, $deg: 45deg) {
+  background-image: linear-gradient($deg, $start-color, $end-color);
+}
+
+@mixin gradient-x-three-colors($start-color: $blue, $mid-color: $purple, $color-stop: 50%, $end-color: $red) {
+  background-image: linear-gradient(to right, $start-color, $mid-color $color-stop, $end-color);
+}
+
+@mixin gradient-y-three-colors($start-color: $blue, $mid-color: $purple, $color-stop: 50%, $end-color: $red) {
+  background-image: linear-gradient($start-color, $mid-color $color-stop, $end-color);
+}
+
+@mixin gradient-radial($inner-color: $gray-700, $outer-color: $gray-800) {
+  background-image: radial-gradient(circle, $inner-color, $outer-color);
+}
+
+@mixin gradient-striped($color: rgba($white, .15), $angle: 45deg) {
+  background-image: linear-gradient($angle, $color 25%, transparent 25%, transparent 50%, $color 50%, $color 75%, transparent 75%, transparent);
+}
+// scss-docs-end gradient-mixins