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/object/README.md

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+# `object`
+
+The `object` crate provides a unified interface to working with object files
+across platforms. It supports reading relocatable object files and executable files,
+and writing COFF/ELF/Mach-O/XCOFF relocatable object files and ELF/PE executable files.
+
+For reading files, it provides multiple levels of support:
+
+* raw struct definitions suitable for zero copy access
+* low level APIs for accessing the raw structs ([example](crates/examples/src/readobj/))
+* a higher level unified API for accessing common features of object files, such
+  as sections and symbols ([example](crates/examples/src/objdump.rs))
+
+Supported file formats for reading: ELF, Mach-O, Windows PE/COFF, Wasm, XCOFF, and Unix archive.
+
+For writing files, it provides:
+
+* low level writers for ELF, PE, and COFF
+* higher level builder for ELF ([example](crates/rewrite/src))
+* a unified API for writing relocatable object files (ELF, Mach-O, COFF, XCOFF)
+  ([example](crates/examples/src/bin/simple_write.rs))
+
+## Example for unified read API
+```rust
+use object::{Object, ObjectSection};
+use std::error::Error;
+use std::fs;
+
+/// Reads a file and displays the name of each section.
+fn main() -> Result<(), Box<dyn Error>> {
+    let binary_data = fs::read("path/to/binary")?;
+    let file = object::File::parse(&*binary_data)?;
+    for section in file.sections() {
+        println!("{}", section.name()?);
+    }
+    Ok(())
+}
+```
+
+See [`crates/examples`](crates/examples) for more examples.
+
+## Minimum Supported Rust Version (MSRV)
+
+Changes to MSRV are considered breaking changes. We are conservative about changing the MSRV,
+but sometimes are required to due to dependencies. The MSRV is 1.65.0.
+
+## License
+
+Licensed under either of
+
+  * Apache License, Version 2.0 ([`LICENSE-APACHE`](./LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
+  * MIT license ([`LICENSE-MIT`](./LICENSE-MIT) or https://opensource.org/licenses/MIT)
+
+at your option.
+
+## Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.