feat: color picker, unified UI styling, filament mismatch detection, Spoolman slot assignment

- Slot color editor: Pickr HSV color picker (offline, served from lib/),
  recent swatches (up to 16, localStorage), copy color from other slot
- Unified axes control panel: XY+Z merged, shared step size + custom mm input
- Language selector moved from header to Settings → Appearance
- Filament mismatch detection blocks Upload-and-Print on material mismatch,
  slot mapper opens automatically
- Spoolman spool-per-slot assignment in AMS status tab and Filaments settings
- Fix: Spoolman sync rate label — 0=end of print, not disabled (Issue #76)
- Fix: lib/ assets served by bridge static handler for offline use
- UI: global unified select + input styling, set-row labels match modal-field

kobrax_moonraker_bridge.py

@@ -142,6 +142,11 @@ _KX_UI_ASSETS: dict[str, str] = {
     "style.css": "text/css",
     "app.js":    "application/javascript",
 }
+# Dateien aus lib/ werden anhand der Extension ausgeliefert (kein Whitelist-Eintrag nötig)
+_KX_UI_LIB_TYPES: dict[str, str] = {
+    ".js":  "application/javascript",
+    ".css": "text/css",
+}
 _KX_UI_TRANSLATION_RE = re.compile(r"^translations/([a-z]{2}(?:-[a-z]{2})?)\.json$")
 
 # Ring-Buffer für Browser-Log-Stream (letzte 200 Einträge)
@@ -3576,6 +3581,12 @@ class KobraXBridge:
 
         if ctype is not None:
             path = os.path.join(_WEB_BASE, "web", "themes", self._ui_theme, name)
+        elif name.startswith("lib/"):
+            ext = os.path.splitext(name)[1].lower()
+            ctype = _KX_UI_LIB_TYPES.get(ext)
+            if not ctype:
+                raise web.HTTPNotFound()
+            path = os.path.join(_WEB_BASE, "web", "themes", self._ui_theme, name)
         else:
             m = _KX_UI_TRANSLATION_RE.match(name)
             if not m: