Add service infrastructure for long-running deployment

- Add configuration system (config/*.exs, OrgGarden.Config)
- Refactor supervision tree with DynamicSupervisor and Registry
- Add OrgGarden.Server for serve mode lifecycle management
- Add health check HTTP endpoints (Bandit/Plug on :9090)
- Add telemetry events for export and watcher operations
- Implement graceful shutdown with SIGTERM handling
- Add Mix Release support with overlay scripts
- Add NixOS module for systemd service deployment
- Update documentation with service usage

rel/env.sh.eex

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+# Release environment configuration
+# This file is evaluated before the release starts
+
+# Disable Erlang distribution (not needed for this application)
+export RELEASE_DISTRIBUTION=none
+
+# Enable shell history in IEx
+export ERL_AFLAGS="-kernel shell_history enabled"
+
+# Set release node name
+export RELEASE_NODE=org_garden
+
+# Log to console by default
+export ELIXIR_ERL_OPTIONS="-noshell"

rel/overlays/bin/org-garden

@@ -0,0 +1,74 @@
+#!/bin/sh
+set -e
+
+# org-garden CLI wrapper
+# Routes commands to the appropriate release entry point
+
+SELF=$(readlink -f "$0" 2>/dev/null || realpath "$0" 2>/dev/null || echo "$0")
+RELEASE_ROOT=$(cd "$(dirname "$SELF")/.." && pwd)
+
+usage() {
+  cat <<EOF
+Usage: org-garden <command> [options]
+
+Commands:
+  serve <notes-dir>    Start development server (long-running)
+  build <notes-dir>    Build static site (one-shot)
+  export <notes-dir>   Export org to markdown (one-shot)
+
+Release commands:
+  daemon               Start as background daemon
+  daemon_iex           Start daemon with IEx attached
+  stop                 Stop running daemon
+  restart              Restart running daemon
+  remote               Connect to running instance
+  pid                  Print PID of running instance
+  version              Print release version
+
+Options:
+  --port <n>           HTTP server port (default: 8080)
+  --ws-port <n>        WebSocket port (default: 3001)
+  --output <path>      Output directory
+  --watch              Watch mode for export command
+
+Environment:
+  NOTES_DIR            Default notes directory
+  OUTPUT_DIR           Default output directory
+  QUARTZ_PATH          Path to Quartz installation
+  ZOTERO_URL           Zotero Better BibTeX URL
+  BIBTEX_FILE          Fallback BibTeX file
+  CITATION_MODE        silent | warn | strict
+EOF
+}
+
+case "${1:-}" in
+  serve)
+    shift
+    exec "$RELEASE_ROOT/bin/org_garden" start -- "$@"
+    ;;
+  build)
+    shift
+    exec "$RELEASE_ROOT/bin/org_garden" eval "OrgGarden.CLI.main([\"build\" | System.argv()])" -- "$@"
+    ;;
+  export)
+    shift
+    exec "$RELEASE_ROOT/bin/org_garden" eval "OrgGarden.CLI.main([\"export\" | System.argv()])" -- "$@"
+    ;;
+  daemon|daemon_iex|stop|restart|remote|pid|version|start|start_iex|eval|rpc)
+    exec "$RELEASE_ROOT/bin/org_garden" "$@"
+    ;;
+  -h|--help|help)
+    usage
+    exit 0
+    ;;
+  "")
+    usage
+    exit 1
+    ;;
+  *)
+    echo "Unknown command: $1" >&2
+    echo "" >&2
+    usage >&2
+    exit 1
+    ;;
+esac