Introduce initial implementation of the vmic CLI with PipeWire integration

- Added `Cargo.toml` to define dependencies and project metadata.
- Implemented core CLI functionality for managing virtual microphones (`create`, `edit`, `delete`, `list`, `route`, and `wipe` commands) using `clap`.
- Integrated `rusqlite` for persistent state storage and `pipewire` to manage PipeWire nodes.
- Ensured graceful handling of feedback loops and system defaults during virtual mic creation and deletion.
- Added error handling via `thiserror` for cleaner error definitions.

src/commands/list.rs

@@ -0,0 +1,62 @@
+use crate::error::Result;
+use crate::pw::PwGraph;
+use crate::state::{self, VmicState};
+use crate::ui;
+
+pub fn run() -> Result<()> {
+    let conn = state::open_db()?;
+    let states = VmicState::list_all(&conn)?;
+    if states.is_empty() {
+        ui::info("No virtual mics created.");
+        return Ok(());
+    }
+
+    let graph = PwGraph::connect().ok();
+
+    for (i, state) in states.iter().enumerate() {
+        let status = liveness(graph.as_ref(), state);
+        let status_colored = if status == "active" { ui::green(&status) } else { ui::yellow(&status) };
+
+        println!("{}", ui::blue(&state.name));
+        println!("  output device:         {}", state.sink_name);
+        println!("  mic device:            {}", state.source_name);
+        println!("  status:                {status_colored}");
+        println!(
+            "  self-monitor loopback: {}",
+            state
+                .loopback_id
+                .map(|id| format!("yes (module {id})"))
+                .unwrap_or_else(|| "no".into())
+        );
+        if let Some(pct) = state.volume_pct {
+            println!("  loopback volume:       {}", ui::blue(&format!("{pct}%")));
+        }
+        if let Some(mic) = &state.mic_source {
+            println!("  mixed source:          {mic}");
+            if let Some(pct) = state.mic_volume_pct {
+                println!("  source volume:         {}", ui::blue(&format!("{pct}%")));
+            }
+        }
+        if i + 1 < states.len() {
+            println!();
+        }
+    }
+
+    Ok(())
+}
+
+/// Checks `sink_node_id`/`mix_node_id` against the live graph snapshot.
+fn liveness(graph: Option<&PwGraph>, state: &VmicState) -> String {
+    let Some(graph) = graph else {
+        return "unknown (could not connect to PipeWire)".to_string();
+    };
+    let nodes = graph.nodes();
+    let sink_alive = state.sink_node_id.is_some_and(|id| nodes.iter().any(|n| n.id == id));
+    let mix_alive = state.mix_node_id.is_some_and(|id| nodes.iter().any(|n| n.id == id));
+    match (sink_alive, mix_alive) {
+        (true, true) => "active".to_string(),
+        (true, false) => "degraded (mix loopback process not found)".to_string(),
+        (false, true) => "degraded (sink loopback process not found)".to_string(),
+        (false, false) => "stale (matching pw-loopback process not found)".to_string(),
+    }
+}