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/esp-hal-embassy/Cargo.toml

@@ -0,0 +1,104 @@
+# 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"
+rust-version = "1.79.0"
+name = "esp-hal-embassy"
+version = "0.5.0"
+build = "build.rs"
+autolib = false
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "Embassy support for esp-hal"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/esp-rs/esp-hal"
+
+[package.metadata.docs.rs]
+default-target = "riscv32imac-unknown-none-elf"
+features = ["esp32c6"]
+
+[lib]
+name = "esp_hal_embassy"
+path = "src/lib.rs"
+
+[dependencies.critical-section]
+version = "1.2.0"
+
+[dependencies.defmt]
+version = "0.3.8"
+optional = true
+
+[dependencies.document-features]
+version = "0.2.10"
+
+[dependencies.embassy-executor]
+version = "0.6.3"
+optional = true
+
+[dependencies.embassy-time-driver]
+version = "0.1.0"
+features = ["tick-hz-1_000_000"]
+
+[dependencies.esp-hal]
+version = "0.22.0"
+
+[dependencies.log]
+version = "0.4.22"
+optional = true
+
+[dependencies.macros]
+version = "0.15.0"
+features = ["embassy"]
+package = "esp-hal-procmacros"
+
+[dependencies.portable-atomic]
+version = "1.9.0"
+
+[dependencies.static_cell]
+version = "2.1.0"
+
+[build-dependencies.esp-build]
+version = "0.1.0"
+
+[build-dependencies.esp-config]
+version = "0.2.0"
+features = ["build"]
+
+[build-dependencies.esp-metadata]
+version = "0.4.0"
+
+[features]
+default = ["executors"]
+defmt = [
+    "dep:defmt",
+    "embassy-executor?/defmt",
+    "esp-hal/defmt",
+]
+esp32 = ["esp-hal/esp32"]
+esp32c2 = ["esp-hal/esp32c2"]
+esp32c3 = ["esp-hal/esp32c3"]
+esp32c6 = ["esp-hal/esp32c6"]
+esp32h2 = ["esp-hal/esp32h2"]
+esp32s2 = ["esp-hal/esp32s2"]
+esp32s3 = ["esp-hal/esp32s3"]
+executors = [
+    "dep:embassy-executor",
+    "esp-hal/__esp_hal_embassy",
+]
+integrated-timers = ["embassy-executor?/integrated-timers"]
+log = ["dep:log"]
+
+[lints.rust]
+unexpected_cfgs = "allow"