feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/lora-phy/Cargo.toml

@@ -0,0 +1,62 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "lora-phy"
+version = "3.0.1"
+description = "A LoRa physical layer implementation enabling utilization of a range of MCU/LoRa board combinations within embedded frameworks supporting embedded-hal-async."
+readme = "README.md"
+keywords = [
+    "lora",
+    "radio",
+    "embedded-hal-async",
+    "iot",
+    "semtech",
+]
+categories = [
+    "embedded",
+    "no-std",
+    "asynchronous",
+]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/embassy-rs/lora-phy"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = [
+    "--cfg",
+    "docsrs",
+]
+
+[dependencies.defmt]
+version = "0.3"
+
+[dependencies.embedded-hal]
+version = "1"
+
+[dependencies.embedded-hal-async]
+version = "1"
+
+[dependencies.lora-modulation]
+version = ">=0.1.2"
+
+[dependencies.lorawan-device]
+version = "0.12"
+features = ["defmt"]
+optional = true
+
+[dependencies.num-traits]
+version = "0.2"
+default-features = false
+
+[features]
+lorawan-radio = ["dep:lorawan-device"]