feat(compose): optional Trino + KairosDB connector overlay

Adds compose.trino.yml as an opt-in overlay applied on top of the core
docker-compose.yml. Brings up a single-node Trino (476) with the
trino-kairosdb-connector (3.0.0-rc1) installed via a one-shot init
service into a named volume, mounted alongside an ExaMon-owned KairosDB
catalog. Matches the Kubernetes overlay shape so connector and Trino
pins move together.

Author: fbeneventi

compose.trino.yml

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+# Optional Trino overlay for the ExaMon Docker Compose stack.
+# Compatibility: trino-kairosdb-connector 3.0.0-rc1, tested with Trino 476.
+# Usage: docker compose -f docker-compose.yml -f compose.trino.yml up -d
+# See deploy/docker/trino/README.md for details.
+
+services:
+  trino-connector-init:
+    image: curlimages/curl:8.10.1
+    command:
+      - sh
+      - -c
+      - |
+        set -eu
+        test -f /plugin/kairosdb-connector.jar || \
+        curl -fsSL -o /plugin/kairosdb-connector.jar \
+          "https://github.com/ExamonHPC/trino-kairosdb-connector/releases/download/3.0.0-rc1/kairosdb-connector-3.0.0-rc1.jar"
+    volumes:
+      - trino_kairosdb_plugin:/plugin
+    networks:
+      - examon_net
+    restart: "no"
+
+  trino:
+    image: trinodb/trino:476
+    depends_on:
+      trino-connector-init:
+        condition: service_completed_successfully
+      kairosdb:
+        condition: service_healthy
+    ports:
+      - "8080:8080"
+    volumes:
+      - trino_kairosdb_plugin:/usr/lib/trino/plugin/kairosdb:ro
+      - ./deploy/docker/trino/catalog:/etc/trino/catalog:ro
+    networks:
+      - examon_net
+    restart: unless-stopped
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "1"
+
+volumes:
+  trino_kairosdb_plugin:

deploy/docker/trino/README.md

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+# Trino overlay for Docker Compose
+
+Optional add-on that brings a single-node Trino with the KairosDB connector
+into the ExaMon Compose stack. Trino stays a separate component: lifecycle,
+upgrades, and tuning are decoupled from the core stack.
+
+## Layout
+
+- `../../../compose.trino.yml` — overlay file applied on top of `docker-compose.yml`.
+- `catalog/examon_ts_timestamps.properties` — KairosDB catalog, mounted into Trino at `/etc/trino/catalog`.
+
+The connector JAR is fetched at startup by a one-shot init service
+(`trino-connector-init`) into a named volume (`trino_kairosdb_plugin`),
+which is then mounted into Trino at `/usr/lib/trino/plugin/kairosdb`. The
+JAR is downloaded once and cached in the volume across restarts.
+
+## Usage
+
+From the repository root, with the core stack already configured:
+
+```bash
+docker compose -f docker-compose.yml -f compose.trino.yml up -d
+```
+
+Trino is reachable on `http://localhost:8080`. Inside the Compose network
+the catalog reaches KairosDB at `http://kairosdb:8083`.
+
+To remove only the Trino overlay (keeping the core stack):
+
+```bash
+docker compose -f docker-compose.yml -f compose.trino.yml stop trino trino-connector-init
+docker compose -f docker-compose.yml -f compose.trino.yml rm -f trino trino-connector-init
+```
+
+## Pin policy
+
+- Trino image tag and connector version are pinned in `compose.trino.yml`.
+- The Kubernetes overlay in `deploy/trino/values-examon.yaml` tracks the
+  same pins; both files should move together on a connector or Trino bump.

deploy/docker/trino/catalog/examon_ts_timestamps.properties

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+connector.name=kairosdb
+kairosdb.url=http://kairosdb:8083
+kairosdb.timestamp.format=TIMESTAMP_TZ
+kairosdb.timestamp.default-start-hours=24