feat: add RGB panel display and GT911 touch config for Waveshare 7"

firmware/components/display.yaml

@@ -1 +1,47 @@
-# placeholder — see task 3/4/5/6
+i2c:
+  - id: i2c_bus
+    sda: GPIO8
+    scl: GPIO9
+    scan: true
+
+ch422g:
+  - id: io_expander
+    i2c_id: i2c_bus
+
+touchscreen:
+  - platform: gt911
+    id: touch_gt911
+    i2c_id: i2c_bus
+    address: 0x5D           # confirmed via Waveshare's documented I2C address map
+    interrupt_pin: GPIO4
+    reset_pin:
+      ch422g: io_expander
+      number: 1              # EXIO1 = TP_RST, per Waveshare pinout
+    display: lcd_display
+
+display:
+  - platform: mipi_rgb
+    id: lcd_display
+    model: WAVESHARE-5-1024X600   # ESPHome's closest built-in preset: same ST7701 chip, data pins,
+                                    # and CH422G reset/enable wiring as this board's 1024x600 panel
+    dimensions:
+      width: 1024
+      height: 600
+      pad_width: 0    # the preset's default width/height (1024x600) don't match its inherited
+      pad_height: 0   # native_width/native_height (800x480 from the base 4.3" model), which makes
+                       # ESPHome's offset math go negative unless pad is forced explicitly here
+    enable_pin:
+      - ch422g: io_expander
+        number: 2              # EXIO2 = DISP (backlight enable) — inherited from the base preset
+      - ch422g: io_expander
+        number: 6              # EXIO6 = LCD_VDD_EN (VCOM enable) — the built-in preset doesn't set
+                                 # this, but the Waveshare wiki confirms VCOM must be driven high on
+                                 # this board or the panel won't display correctly. Added explicitly.
+    lambda: |-
+      it.fill(Color::BLACK);
+      it.print(512, 300, id(font_label), TextAlign::CENTER, "Thermostat — Phase 1 OK");
+
+font:
+  - file: "gfonts://Roboto"
+    id: font_label
+    size: 32