Initial commit: PocketBase Docker setup (root & rootless variants)

Add Dockerfiles, Compose stacks, and entrypoints for running PocketBase
in both root and rootless container configurations, plus .env.example
documenting version, port, superuser bootstrap, and encryption settings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,31 @@
+# Copy this file to `.env` and adjust as needed:
+#   cp .env.example .env
+# Compose reads `.env` automatically. Keep `.env` OUT of version control.
+
+# ── General ───────────────────────────────────────────────────────────
+# PocketBase version to build (must match a published release tag, without the leading "v")
+PB_VERSION=0.39.7
+
+# Name of the running container
+CONTAINER_NAME=pocketbase
+
+# Port PocketBase listens on (used both inside the container and for the host mapping)
+PB_PORT=8080
+
+# Port for the root variant (only used with `docker compose --profile root up`)
+PB_PORT_ROOT=8081
+
+# ── Superuser bootstrap ───────────────────────────────────────────────
+# On every start the entrypoint checks whether PB_ADMIN_EMAIL already exists:
+#   • exists     → nothing happens (PB_ADMIN_PASSWORD is ignored/optional)
+#   • missing    → the superuser is created using PB_ADMIN_PASSWORD (required in that case)
+# No defaults. Leave blank to skip bootstrapping entirely.
+PB_ADMIN_EMAIL=
+PB_ADMIN_PASSWORD=
+
+# ── Encryption ────────────────────────────────────────────────────────
+# Encrypts the application settings stored in PocketBase's database.
+# Must be EXACTLY 32 characters. Leave blank to disable.
+# Generate one with:  openssl rand -hex 16
+# Docs: https://pocketbase.io/docs/going-to-production/#enable-settings-encryption
+PB_ENCRYPTION_KEY=