docs: describe current state only, and fill in the stub READMEs

Drop the history and roadmap asides: which services predate the collection's
conventions, the unwired Open Web UI plan, the generic clone-and-troubleshoot
boilerplate. Services that publish ports or set `restart:` now simply say so.

couchbase, openvpn-as and traffmonetizer had two-line READMEs; give them the
ports, variables and storage the root README promises. traffmonetizer reads
${TOKEN} and had no .env.example, so add one.

traffmonetizer/.env.example

@@ -0,0 +1,6 @@
+# Copy to .env and fill in. Never commit .env.
+#
+#   cp .env.example .env
+
+# Application token from the TraffMonetizer dashboard, under "Your token".
+TOKEN=

traffmonetizer/README.md

@@ -1,2 +1,20 @@
-# traffmonetizer-docker-compose
-Sample docker-compose.yml for TraffMonetizer
+# traffmonetizer
+
+[TraffMonetizer](https://traffmonetizer.com) bandwidth-sharing client.
+
+Uses `docker-compose.yml`, and sets `restart: always` and
+`container_name: tm` — unlike the platform-managed services described in the
+[root README](../README.md). Publishes no ports; the client only makes outbound
+connections.
+
+The image tag is `arm64v8`. Change it to match the host architecture.
+
+## Environment
+
+| Variable | Purpose |
+| --- | --- |
+| `TOKEN` | Application token from the TraffMonetizer dashboard. Passed both as an environment variable and on the `start accept --token` command line. |
+
+## Storage
+
+None — the client keeps no state worth persisting.