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/pw/mod.rs

@@ -0,0 +1,28 @@
+//! PipeWire control, split into three modules:
+//!
+//! - `graph`    - live graph control (link/unlink ports, break feedback
+//!                rings, node/port/link introspection) via `pipewire-rs`,
+//!                using only numeric object ids and this program's own
+//!                ASCII node names.
+//! - `loopback` - creates/destroys the two chained loopback stages and the
+//!                self-monitor loopback, built on top of `graph`.
+//! - `text`     - byte-safe text matching (`pactl` subprocess output) for
+//!                anything that has to match against human-authored,
+//!                possibly-multibyte device names/descriptions.
+//!
+//! Module *lifecycle* (spawning/loading the loopback stages and the
+//! self-monitor) can't go through `graph`: `pw_context_load_module` loads a
+//! module into the *calling process's own* context, which then has to keep
+//! running its main loop forever for the module's nodes to keep producing
+//! audio - that's what `pw-loopback` itself is. A one-shot CLI invocation
+//! can't be that persistent host, so the two chained stages stay
+//! `pw-loopback` subprocesses (tracked by pid), and the self-monitor stays a
+//! `pactl load-module`/`unload-module` call. Everything downstream of
+//! that - linking, unlinking, ring-breaking, liveness - is native
+//! `pipewire-rs` via `graph`.
+
+pub mod graph;
+pub mod loopback;
+pub mod text;
+
+pub use graph::PwGraph;