Add support for --loopback-no-mix flag and topology synchronization

- Introduced the `--loopback-no-mix` flag to control 2-node vs 4-node loopback topologies.
- Updated topology handling logic to recompute and migrate as needed based on loopback flags.
- Enhanced database schema to include `loopback_no_mix` with automatic migration for backward compatibility.
- Refactored `create`, `edit`, and `route` commands to integrate new topology management capabilities.
- Improved `list` command output to include architecture details.

src/pw/text.rs

@@ -188,6 +188,64 @@ fn parse_sink_input_for_module(text: &str, module_id: u32) -> Option<u32> {
     None
 }
 
+/// Numeric pulse-side id for `name` within `kind` ("sinks" or "sources"),
+/// via `pactl list short <kind>` - same id/name column layout used by
+/// `match_source`'s numeric branch and `wipe::first_non_vmic`.
+fn resolve_pulse_id(kind: &str, name: &str) -> Result<Option<u32>> {
+    let output = Command::new("pactl").args(["list", "short", kind]).output()?;
+    Ok(String::from_utf8_lossy(&output.stdout)
+        .lines()
+        .find_map(|l| {
+            let mut cols = l.split_whitespace();
+            let id = cols.next()?.parse::<u32>().ok()?;
+            (cols.next()? == name).then_some(id)
+        }))
+}
+
+/// Ids of every sink-input currently targeting `sink_name`. Used by
+/// `commands::topology::migrate` to snapshot stream routing before a
+/// migration recreates the sink node, so they can be moved back afterward.
+pub fn sink_inputs_on(sink_name: &str) -> Result<Vec<u32>> {
+    let Some(id) = resolve_pulse_id("sinks", sink_name)? else {
+        return Ok(Vec::new());
+    };
+    let output = Command::new("pactl").args(["list", "sink-inputs"]).output()?;
+    Ok(parse_ids_matching(&String::from_utf8_lossy(&output.stdout), "Sink Input #", "Sink: ", id))
+}
+
+/// Ids of every source-output currently reading from `source_name`. See
+/// `sink_inputs_on`.
+pub fn source_outputs_on(source_name: &str) -> Result<Vec<u32>> {
+    let Some(id) = resolve_pulse_id("sources", source_name)? else {
+        return Ok(Vec::new());
+    };
+    let output = Command::new("pactl").args(["list", "source-outputs"]).output()?;
+    Ok(parse_ids_matching(&String::from_utf8_lossy(&output.stdout), "Source Output #", "Source: ", id))
+}
+
+/// Ids of every block (headed by `header_prefix<id>`) whose `key_prefix<id>`
+/// property line equals `target_id`.
+fn parse_ids_matching(text: &str, header_prefix: &str, key_prefix: &str, target_id: u32) -> Vec<u32> {
+    let mut ids = Vec::new();
+    let mut current_id: Option<u32> = None;
+
+    for line in text.lines() {
+        if let Some(rest) = line.strip_prefix(header_prefix) {
+            current_id = rest.trim().parse().ok();
+            continue;
+        }
+        let trimmed = line.trim_start();
+        if let Some(rest) = trimmed.strip_prefix(key_prefix) {
+            if rest.trim().parse::<u32>().ok() == Some(target_id) {
+                if let Some(id) = current_id {
+                    ids.push(id);
+                }
+            }
+        }
+    }
+    ids
+}
+
 /// Every `module-loopback` whose `Argument:` line mentions a `vmic_` node,
 /// tracked in state or not.
 pub fn list_vmic_loopback_module_ids() -> Result<Vec<u32>> {
@@ -238,6 +296,31 @@ Sink Input #12
         assert_eq!(parse_sink_input_for_module(text, 99), None);
     }
 
+    #[test]
+    fn finds_sink_inputs_targeting_sink() {
+        let text = "\
+Sink Input #10
+\tSink: 65
+Sink Input #11
+\tSink: 99
+Sink Input #12
+\tSink: 65
+";
+        assert_eq!(parse_ids_matching(text, "Sink Input #", "Sink: ", 65), vec![10, 12]);
+        assert_eq!(parse_ids_matching(text, "Sink Input #", "Sink: ", 1), Vec::<u32>::new());
+    }
+
+    #[test]
+    fn finds_source_outputs_targeting_source() {
+        let text = "\
+Source Output #20
+\tSource: 3
+Source Output #21
+\tSource: 4
+";
+        assert_eq!(parse_ids_matching(text, "Source Output #", "Source: ", 3), vec![20]);
+    }
+
     #[test]
     fn lists_only_vmic_loopback_modules() {
         let text = "\