Add theme switchers: Admin UI (A/B/C) + Display (5 themes)

Admin UI: Dark Minimal / Retro Terminal / Warm Editorial via header buttons
Display: Classic White / Dark / Sepia / Nord / Terminal via Settings tab
Both switchers persist via localStorage / config.json

dashboard.py

@@ -260,6 +260,46 @@ class Dashboard:
             self.items = items
             self.widgets = widgets
             self.config_mtime = CONFIG_PATH.stat().st_mtime if CONFIG_PATH.exists() else 0
+            self.display_theme = cfg.get("display_theme", "default")
+
+    def apply_display_theme(self, img):
+        """Überschreibe BG/FG des Bildes je nach display_theme."""
+        theme = self.display_theme if hasattr(self, 'display_theme') else "default"
+        if theme == "default":
+            return
+        # Map theme → palette overrides
+        # For now only BG/FG swap makes sense for ACeP
+        # dark/terminal invert, sepia/nord just shift
+        themed_palette = {
+            "dark":    {"bg": (17, 17, 17),  "fg": (240, 240, 240)},
+            "sepia":   {"bg": (244, 236, 216), "fg": (91, 70, 54)},
+            "nord":    {"bg": (236, 239, 244), "fg": (46, 52, 64)},
+            "terminal": {"bg": (13, 13, 0),     "fg": (232, 200, 64)},
+        }
+        if theme not in themed_palette:
+            return
+        overrides = themed_palette[theme]
+        # Flood-fill BG areas with theme BG (simple but effective for flat designs)
+        # We do an Image.paste to recolor the BG — for now just swap BG pixel
+        bg_r, bg_g, bg_b = overrides["bg"]
+        fg_color = overrides["fg"]
+        # Replace WHITE pixels with theme BG, replace BLACK pixels with theme FG
+        data = img.convert("RGB")
+        w, h = img.size
+        # Direct pixel access — only for flat BG designs
+        for y in range(h):
+            for x in range(w):
+                r, g, b = data.getpixel((x, y))
+                if r > 240 and g > 240 and b > 240:
+                    # WHITE → theme bg
+                    data.putpixel((x, y), (bg_r, bg_g, bg_b))
+                elif r < 15 and g < 15 and b < 15:
+                    # BLACK → theme fg
+                    data.putpixel((x, y), fg_color)
+        # Convert back to palette-compatible mode
+        pal_img = img.copy()
+        pal_img.paste(data)
+        return pal_img
 
     def maybe_reload_config(self):
         if not CONFIG_PATH.exists():
@@ -288,6 +328,10 @@ class Dashboard:
             items = list(self.items)
             widgets = list(self.widgets)
         img = render_full(items, widgets, self.fonts)
+        # Apply display theme (BG/FG color remap) — admin preview also uses this
+        themed = self.apply_display_theme(img)
+        if themed is not None:
+            return themed
         return img
 
     def display(self, img: Image.Image):