feat: add Caddy reverse proxy with auto HTTPS for LAN access and auto-derive WebSocket URL (#863)

* feat: add Caddy reverse proxy with auto HTTPS for LAN access and auto-derive WebSocket URL

Add a Caddy service to docker-compose.standalone.yml that provides automatic
HTTPS with local certificates, enabling secure access to both the frontend
and API from the local network through a single entrypoint.

Backend changes:
- Add ROOT_PATH setting to FastAPI so the API can be served under /api prefix
- Route frontend and API (/server-api) through Caddy reverse proxy

Frontend changes:
- Support WEBSOCKET_URL=auto to derive the WebSocket URL from API_URL
  automatically, using the page protocol (http→ws, https→wss) and host
- Make WEBSOCKET_URL env var optional instead of required

* style: pre-commit

* fix: make standalone compose self-contained (drop !reset dependency)

docker-compose.standalone.yml used !reset YAML tags to clear
network_mode and volumes from the base compose. !reset requires
Compose v2.24+ and breaks on Colima + brew-installed compose.

Rewrite as a fully self-contained file with all services defined
directly (server, worker, beat, redis, postgres, web, garage, cpu,
gpu-nvidia, ollama, ollama-cpu). No longer overlays docker-compose.yml.

Update setup-standalone.sh compose_cmd() to use only the standalone
file instead of both files.

* fix: update standalone docs to match self-contained compose usage

---------

Co-authored-by: Igor Loskutov <igor.loskutoff@gmail.com>

www/app/lib/clientEnv.ts

@@ -2,6 +2,7 @@ import {
   assertExists,
   assertExistsAndNonEmptyString,
   NonEmptyString,
+  parseMaybeNonEmptyString,
   parseNonEmptyString,
 } from "./utils";
 import { isBuildPhase } from "./next";
@@ -74,14 +75,14 @@ export const getClientEnvServer = (): ClientEnvCommon => {
   if (isBuildPhase) {
     return {
       API_URL: getNextEnvVar("API_URL"),
-      WEBSOCKET_URL: getNextEnvVar("WEBSOCKET_URL"),
+      WEBSOCKET_URL: parseMaybeNonEmptyString(process.env.WEBSOCKET_URL ?? ""),
       ...features,
     };
   }
 
   clientEnv = {
     API_URL: getNextEnvVar("API_URL"),
-    WEBSOCKET_URL: getNextEnvVar("WEBSOCKET_URL"),
+    WEBSOCKET_URL: parseMaybeNonEmptyString(process.env.WEBSOCKET_URL ?? ""),
     ...features,
   };
   return clientEnv;