feat: add Mosaic Graphics support and fix char rendering

- Added Mosaic Picker dialog with visual previews
- Added 'Graphics' mode toggle to UI
- Implemented status bar mode indicator (Text/Graphics)
- Corrected English character mapping for 0x60 to Hyphen (-)
- Verified German and Swedish/Finnish character sets against ETSI spec

src/teletext/renderer.py

@@ -53,7 +53,7 @@ COLORS = [
 ]
 
 class TeletextCanvas(QWidget):
-    cursorChanged = pyqtSignal(int, int, int) # x, y, byte_val
+    cursorChanged = pyqtSignal(int, int, int, bool) # x, y, byte_val, is_graphics
 
     def __init__(self, parent=None):
         super().__init__(parent)
@@ -83,6 +83,7 @@ class TeletextCanvas(QWidget):
         self.cursor_x = 0
         self.cursor_y = 0
         self.cursor_visible = True
+        self.cursor_is_graphics = False # Tracked during draw
         # Blinking cursor timer could be added, for now static inverted is fine or toggle on timer elsewhere
 
     def get_byte_at(self, x, y):
@@ -103,7 +104,7 @@ class TeletextCanvas(QWidget):
 
     def emit_cursor_change(self):
         val = self.get_byte_at(self.cursor_x, self.cursor_y)
-        self.cursorChanged.emit(self.cursor_x, self.cursor_y, val)
+        self.cursorChanged.emit(self.cursor_x, self.cursor_y, val, self.cursor_is_graphics)
 
     def set_cursor(self, x, y):
         self.cursor_x = max(0, min(self.cols - 1, x))
@@ -329,6 +330,10 @@ class TeletextCanvas(QWidget):
             if double_height and not is_occluded:
                 next_occlusion_mask[c] = True
 
+            # Capture cursor state if this is the cursor position
+            if c == self.cursor_x and row == self.cursor_y:
+                self.cursor_is_graphics = graphics_mode
+
             # If occluded, do not draw anything for this cell
             if is_occluded:
                 continue