Initial Meterbox commit with boot disk usage metric.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/config.rs

@@ -0,0 +1,46 @@
+use std::path::PathBuf;
+
+use clap::Parser;
+
+#[derive(Debug, Clone, Parser)]
+#[command(name = "meterbox", about = "Host resource usage dashboard")]
+pub struct Config {
+    /// Bind address — default localhost only (safe behind Caddy/Rathole)
+    #[arg(long, env = "METERBOX_LISTEN", default_value = "127.0.0.1:8787")]
+    pub listen: String,
+
+    /// SQLite database path
+    #[arg(long, env = "METERBOX_DB", default_value = "data/meterbox.db")]
+    pub db_path: PathBuf,
+
+    /// Directory with built React assets
+    #[arg(long, env = "METERBOX_STATIC", default_value = "frontend/dist")]
+    pub static_dir: PathBuf,
+
+    /// Sample interval in seconds
+    #[arg(long, env = "METERBOX_INTERVAL_SECS", default_value_t = 30)]
+    pub interval_secs: u64,
+
+    /// Retain samples for this many days (max ~3 months)
+    #[arg(long, env = "METERBOX_RETENTION_DAYS", default_value_t = 90)]
+    pub retention_days: i64,
+
+    /// Hard cap for SQLite on-disk size (main + WAL + SHM), bytes. Default 10 GiB.
+    #[arg(long, env = "METERBOX_MAX_DB_BYTES", default_value_t = 10 * 1024 * 1024 * 1024)]
+    pub max_db_bytes: u64,
+
+    /// How often the cleanup job runs (seconds). Default 1 hour.
+    #[arg(long, env = "METERBOX_CLEANUP_INTERVAL_SECS", default_value_t = 3600)]
+    pub cleanup_interval_secs: u64,
+}
+
+impl Config {
+    pub fn ensure_dirs(&self) -> anyhow::Result<()> {
+        if let Some(parent) = self.db_path.parent() {
+            if !parent.as_os_str().is_empty() {
+                std::fs::create_dir_all(parent)?;
+            }
+        }
+        Ok(())
+    }
+}