Add logging service

New Go program (logger/) that:
- Accepts POSTed JSON log messages via POST /log
- Stores last N messages in a ring buffer (default 1M)
- Retrieves logs via GET /logs with limit/before/after filters
- Shows status via GET /status

Also updates express/logging.ts to POST messages to the logger service.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

express/logging.ts

@@ -32,15 +32,39 @@ type FilterArgument = {
     match?: (string | RegExp)[];
 };
 
-const log = (_message: Message) => {
-    // WRITEME
-    console.log(
-        `will POST a message to ${cli.logAddress.host}:${cli.logAddress.port}`,
-    );
+const loggerUrl = `http://${cli.logAddress.host}:${cli.logAddress.port}`;
+
+const log = (message: Message) => {
+    const payload = {
+        timestamp: message.timestamp ?? Date.now(),
+        source: message.source,
+        text: message.text,
+    };
+
+    fetch(`${loggerUrl}/log`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(payload),
+    }).catch((err) => {
+        console.error("[logging] Failed to send log:", err.message);
+    });
 };
 
-const getLogs = (filter: FilterArgument) => {
-    // WRITEME
+const getLogs = async (filter: FilterArgument): Promise<Message[]> => {
+    const params = new URLSearchParams();
+    if (filter.limit) {
+        params.set("limit", String(filter.limit));
+    }
+    if (filter.before) {
+-        params.set("before", String(filter.before));
+    }
+    if (filter.after) {
+        params.set("after", String(filter.after));
+    }
+
+    const url = `${loggerUrl}/logs?${params.toString()}`;
+    const response = await fetch(url);
+    return response.json();
 };
 
 // FIXME: there's scope for more specialized functions although they