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/enumset/Cargo.toml

@@ -0,0 +1,102 @@
+# 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 = "1.61"
+name = "enumset"
+version = "1.1.10"
+authors = ["Alissa Rao <aura@aura.moe>"]
+build = false
+autolib = false
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "A library for creating compact sets of enums."
+documentation = "https://docs.rs/enumset/"
+readme = "README.md"
+keywords = [
+    "enum",
+    "bitset",
+]
+categories = ["data-structures"]
+license = "MIT/Apache-2.0"
+repository = "https://github.com/Lymia/enumset"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = [
+    "--cfg",
+    "docsrs",
+]
+
+[badges.maintenance]
+status = "actively-developed"
+
+[badges.travis-ci]
+branch = "master"
+repository = "Lymia/enumset"
+
+[features]
+alloc = []
+proc-macro-crate = ["enumset_derive/proc-macro-crate"]
+serde2 = ["enumset_derive/serde2_deprecation_warning"]
+std = [
+    "alloc",
+    "enumset_derive/proc-macro-crate",
+    "enumset_derive/std_deprecation_warning",
+]
+
+[lib]
+name = "enumset"
+path = "src/lib.rs"
+
+[[test]]
+name = "bitset_basic_ops"
+path = "tests/bitset_basic_ops.rs"
+
+[[test]]
+name = "bitset_conversions"
+path = "tests/bitset_conversions.rs"
+
+[[test]]
+name = "bitset_explicit_repr"
+path = "tests/bitset_explicit_repr.rs"
+
+[[test]]
+name = "bitset_serde_ops"
+path = "tests/bitset_serde_ops.rs"
+
+[dependencies.defmt]
+version = "1"
+optional = true
+
+[dependencies.enumset_derive]
+version = "0.14.0"
+
+[dependencies.serde]
+version = "1"
+optional = true
+default-features = false
+
+[dev-dependencies.bincode]
+version = "1"
+features = ["i128"]
+
+[dev-dependencies.rustversion]
+version = "1.0"
+
+[dev-dependencies.serde_derive]
+version = "1"
+
+[dev-dependencies.serde_json]
+version = "1"