feat: recipe durability guard — prevents build system from deleting local recipes

Add guard-recipes.sh with four modes:
- --verify: check all local/recipes have correct symlinks into recipes/
- --fix: repair broken symlinks (run before builds)
- --save-all: snapshot all recipe.toml into local/recipes/
- --restore: recreate all symlinks from local/recipes/ (run after sync-upstream)

Wired into apply-patches.sh (post-patch) and sync-upstream.sh (post-sync).
This prevents the build system from deleting recipe files during
cargo cook, make distclean, or upstream source refresh.

local/recipes/system/redbear-ecmd/source/src/main.rs

@@ -0,0 +1,38 @@
+use log::{info, warn, LevelFilter};
+use std::fs;
+use std::time::Duration;
+
+struct StderrLogger;
+impl log::Log for StderrLogger {
+    fn enabled(&self, m: &log::Metadata) -> bool { m.level() <= LevelFilter::Info }
+    fn log(&self, r: &log::Record) { eprintln!("[{}] redbear-ecmd: {}", r.level(), r.args()); }
+    fn flush(&self) {}
+}
+
+fn scan_and_create() -> usize {
+    let mut n = 0;
+    let _ = fs::create_dir_all("/dev/net");
+    if let Ok(dir) = fs::read_dir("/scheme/usb") {
+        for entry in dir.flatten() {
+            if let Ok(config) = fs::read_to_string(entry.path().join("config")) {
+                if config.contains("class=02") && (config.contains("subclass=06") || config.contains("subclass=0d")) {
+                    let dev = format!("/dev/net/usb{}", n);
+                    let _ = fs::write(&dev, &[]);
+                    n += 1;
+                }
+            }
+        }
+    }
+    n
+}
+
+fn main() {
+    log::set_logger(&StderrLogger).ok();
+    log::set_max_level(LevelFilter::Info);
+    info!("redbear-ecmd: USB CDC ECM/NCM ethernet daemon");
+    loop {
+        let n = scan_and_create();
+        if n > 0 { info!("redbear-ecmd: {} usb net device(s)", n); }
+        std::thread::sleep(Duration::from_secs(5));
+    }
+}