feat: add Rust reverse proxy with JSON logging

- Axum-based API server with Unix socket and TCP support
- Custom tracing formatters for Railway-compatible JSON logs
- SvelteKit hooks and Vite plugin for unified logging
- Justfile updated for concurrent dev workflow with hl log viewer

web/src/lib/api.ts

@@ -0,0 +1,75 @@
+import { getLogger } from "@logtape/logtape";
+import { env } from "$env/dynamic/private";
+
+const logger = getLogger(["ssr", "lib", "api"]);
+
+// Compute upstream configuration once at module load
+const upstreamUrl = env.UPSTREAM_URL;
+const isUnixSocket =
+  upstreamUrl?.startsWith("/") || upstreamUrl?.startsWith("./");
+const baseUrl = isUnixSocket ? "http://localhost" : upstreamUrl;
+
+/**
+ * Fetch utility for calling the Rust backend API.
+ * Automatically prefixes requests with the upstream URL from environment.
+ * Supports both HTTP URLs and Unix socket paths.
+ *
+ * Connection pooling and keep-alive are handled automatically by Bun.
+ * Default timeout is 30 seconds unless overridden via init.signal.
+ */
+export async function apiFetch<T>(
+  path: string,
+  init?: RequestInit,
+): Promise<T> {
+  if (!upstreamUrl) {
+    logger.error("UPSTREAM_URL environment variable not set");
+    throw new Error("UPSTREAM_URL environment variable not set");
+  }
+
+  const url = `${baseUrl}${path}`;
+  const method = init?.method ?? "GET";
+
+  // Build fetch options with 30s default timeout and unix socket support
+  const fetchOptions: RequestInit & { unix?: string } = {
+    ...init,
+    // Respect caller-provided signal, otherwise default to 30s timeout
+    signal: init?.signal ?? AbortSignal.timeout(30_000),
+  };
+
+  if (isUnixSocket) {
+    fetchOptions.unix = upstreamUrl;
+  }
+
+  logger.debug("API request", {
+    method,
+    url,
+    path,
+    isUnixSocket,
+    upstreamUrl,
+  });
+
+  try {
+    const response = await fetch(url, fetchOptions);
+
+    if (!response.ok) {
+      logger.error("API request failed", {
+        method,
+        url,
+        status: response.status,
+        statusText: response.statusText,
+      });
+      throw new Error(`API error: ${response.status} ${response.statusText}`);
+    }
+
+    const data = await response.json();
+    logger.debug("API response", { method, url, status: response.status });
+    return data;
+  } catch (error) {
+    logger.error("API request exception", {
+      method,
+      url,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    throw error;
+  }
+}