S3+S4: user param auth, static file serving, Docker deploy config

- replace hardcoded benji with ?user= query param
- add GET /api/users and GET /api/me?user= endpoints
- serve frontend static files via tower-http ServeDir
- add multi-stage Dockerfile (Rust + Vite → single image)
- add docker-compose.yml + Caddyfile for apes.unslope.com
- frontend: getCurrentUsername() from URL param → localStorage
- sidebar shows current user

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/colony/src/App.tsx

@@ -1,7 +1,7 @@
 import { useCallback, useEffect, useRef, useState } from "react";
 import type { Channel } from "@/types/Channel";
 import type { Message } from "@/types/Message";
-import { getChannels, getMessages } from "@/api";
+import { getChannels, getMessages, getCurrentUsername } from "@/api";
 import { ChannelSidebar } from "@/components/ChannelSidebar";
 import { MessageItem } from "@/components/MessageItem";
 import { ComposeBox } from "@/components/ComposeBox";

ui/colony/src/api.ts

@@ -1,22 +1,46 @@
 import type { Channel } from "./types/Channel";
 import type { Message } from "./types/Message";
+import type { User } from "./types/User";
 import type { CreateChannel } from "./types/CreateChannel";
 import type { PostMessage } from "./types/PostMessage";
 
 const BASE = "/api";
 
+// Get current user from URL param or localStorage
+export function getCurrentUsername(): string {
+  const url = new URL(window.location.href);
+  const param = url.searchParams.get("user");
+  if (param) {
+    localStorage.setItem("colony_user", param);
+    return param;
+  }
+  return localStorage.getItem("colony_user") || "benji";
+}
+
+function userQuery(): string {
+  return `user=${encodeURIComponent(getCurrentUsername())}`;
+}
+
 async function json<T>(res: Response): Promise<T> {
   if (!res.ok) throw new Error(`${res.status}: ${await res.text()}`);
   return res.json();
 }
 
+export async function getMe(): Promise<User> {
+  return json(await fetch(`${BASE}/me?${userQuery()}`));
+}
+
+export async function getUsers(): Promise<User[]> {
+  return json(await fetch(`${BASE}/users`));
+}
+
 export async function getChannels(): Promise<Channel[]> {
   return json(await fetch(`${BASE}/channels`));
 }
 
 export async function createChannel(body: CreateChannel): Promise<Channel> {
   return json(
-    await fetch(`${BASE}/channels`, {
+    await fetch(`${BASE}/channels?${userQuery()}`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify(body),
@@ -26,10 +50,10 @@ export async function createChannel(body: CreateChannel): Promise<Channel> {
 
 export async function getMessages(
   channelId: string,
-  params?: { since?: string; type?: string; user_id?: string },
+  params?: { after_seq?: number; type?: string; user_id?: string },
 ): Promise<Message[]> {
   const query = new URLSearchParams();
-  if (params?.since) query.set("since", params.since);
+  if (params?.after_seq) query.set("after_seq", String(params.after_seq));
   if (params?.type) query.set("type", params.type);
   if (params?.user_id) query.set("user_id", params.user_id);
   const qs = query.toString();
@@ -43,7 +67,7 @@ export async function postMessage(
   body: PostMessage,
 ): Promise<Message> {
   return json(
-    await fetch(`${BASE}/channels/${channelId}/messages`, {
+    await fetch(`${BASE}/channels/${channelId}/messages?${userQuery()}`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify(body),

ui/colony/src/components/ChannelSidebar.tsx

@@ -1,6 +1,6 @@
 import { useState } from "react";
 import type { Channel } from "@/types/Channel";
-import { createChannel } from "@/api";
+import { createChannel, getCurrentUsername } from "@/api";
 
 interface Props {
   channels: Channel[];
@@ -61,6 +61,12 @@ export function ChannelSidebar({
         ))}
       </div>
 
+      {/* Current user */}
+      <div className="px-3 py-2 border-t border-sidebar-border text-[11px]">
+        <span className="text-muted-foreground">logged in as </span>
+        <span className="font-bold text-foreground">{getCurrentUsername()}</span>
+      </div>
+
       {/* New channel input */}
       <div className="p-2 border-t border-sidebar-border">
         <input