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/bytemuck/Cargo.toml

@@ -0,0 +1,153 @@
+# 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 = "2018"
+name = "bytemuck"
+version = "1.25.0"
+authors = ["Lokathor <zefria@gmail.com>"]
+build = false
+exclude = [
+    "/pedantic.bat",
+    "derive/",
+    "contiguous_bitset/",
+]
+autolib = false
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "A crate for mucking around with piles of bytes."
+readme = "README.md"
+keywords = [
+    "transmute",
+    "bytes",
+    "casting",
+]
+categories = [
+    "encoding",
+    "no-std",
+]
+license = "Zlib OR Apache-2.0 OR MIT"
+repository = "https://github.com/Lokathor/bytemuck"
+
+[package.metadata.docs.rs]
+features = [
+    "nightly_docs",
+    "latest_stable_rust",
+    "extern_crate_alloc",
+    "extern_crate_std",
+]
+
+[package.metadata.playground]
+features = [
+    "latest_stable_rust",
+    "extern_crate_alloc",
+    "extern_crate_std",
+]
+
+[features]
+aarch64_simd = []
+align_offset = []
+alloc_uninit = []
+avx512_simd = []
+const_zeroed = []
+derive = ["bytemuck_derive"]
+extern_crate_alloc = []
+extern_crate_std = ["extern_crate_alloc"]
+impl_core_error = []
+latest_stable_rust = [
+    "aarch64_simd",
+    "avx512_simd",
+    "align_offset",
+    "alloc_uninit",
+    "const_zeroed",
+    "derive",
+    "impl_core_error",
+    "min_const_generics",
+    "must_cast",
+    "must_cast_extra",
+    "pod_saturating",
+    "track_caller",
+    "transparentwrapper_extra",
+    "wasm_simd",
+    "zeroable_atomics",
+    "zeroable_maybe_uninit",
+    "zeroable_unwind_fn",
+]
+min_const_generics = []
+must_cast = []
+must_cast_extra = ["must_cast"]
+nightly_docs = []
+nightly_float = []
+nightly_portable_simd = ["rustversion"]
+nightly_stdsimd = []
+pod_saturating = []
+track_caller = []
+transparentwrapper_extra = []
+unsound_ptr_pod_impl = []
+wasm_simd = []
+zeroable_atomics = []
+zeroable_maybe_uninit = []
+zeroable_unwind_fn = []
+
+[lib]
+name = "bytemuck"
+path = "src/lib.rs"
+
+[[test]]
+name = "array_tests"
+path = "tests/array_tests.rs"
+
+[[test]]
+name = "cast_slice_tests"
+path = "tests/cast_slice_tests.rs"
+
+[[test]]
+name = "checked_tests"
+path = "tests/checked_tests.rs"
+
+[[test]]
+name = "derive"
+path = "tests/derive.rs"
+
+[[test]]
+name = "doc_tests"
+path = "tests/doc_tests.rs"
+
+[[test]]
+name = "offset_of_tests"
+path = "tests/offset_of_tests.rs"
+
+[[test]]
+name = "std_tests"
+path = "tests/std_tests.rs"
+
+[[test]]
+name = "transparent"
+path = "tests/transparent.rs"
+
+[[test]]
+name = "wrapper_forgets"
+path = "tests/wrapper_forgets.rs"
+
+[dependencies.bytemuck_derive]
+version = "1.10.2"
+optional = true
+
+[dependencies.rustversion]
+version = "1.0.22"
+optional = true
+
+[lints.rust.unexpected_cfgs]
+level = "deny"
+priority = 0
+check-cfg = ['cfg(target_arch, values("spirv"))']