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

lib/org_garden/cli.ex

@@ -48,6 +48,8 @@ defmodule OrgGarden.CLI do
 
   require Logger
 
+  alias OrgGarden.Config
+
   @transforms [OrgGarden.Transforms.Citations]
 
   def main(argv) do
@@ -70,31 +72,36 @@ defmodule OrgGarden.CLI do
   def handle_serve(argv) do
     require_quartz_env()
     {notes_dir, output_dir, content_dir, opts} = parse_serve_args(argv)
-    pipeline_opts = build_pipeline_opts()
-
-    # Initial batch export
-    wipe(content_dir)
-    export_all(notes_dir, output_dir)
-    run_pipeline(content_dir, pipeline_opts)
-    generate_index(content_dir)
 
     IO.puts("==> Starting development server...")
 
-    {:ok, _pid} =
-      OrgGarden.Supervisor.start_link(
-        notes_dir: notes_dir,
-        output_dir: output_dir,
-        content_dir: content_dir,
-        pipeline_opts: pipeline_opts,
-        transforms: @transforms,
-        port: opts[:port] || 8080,
-        ws_port: opts[:ws_port] || 3001
-      )
+    case OrgGarden.Server.start_link(
+           notes_dir: notes_dir,
+           output_dir: output_dir,
+           content_dir: content_dir,
+           port: opts[:port],
+           ws_port: opts[:ws_port]
+         ) do
+      {:ok, pid} ->
+        IO.puts("==> Server running at http://localhost:#{opts[:port] || Config.get(:http_port, 8080)}")
+        IO.puts("==> Watching #{notes_dir} for changes (Ctrl+C to stop)")
 
-    IO.puts("==> Server running at http://localhost:#{opts[:port] || 8080}")
-    IO.puts("==> Watching #{notes_dir} for changes (Ctrl+C to stop)")
+        # Wait for server to exit
+        ref = Process.monitor(pid)
 
-    Process.sleep(:infinity)
+        receive do
+          {:DOWN, ^ref, :process, ^pid, reason} ->
+            case reason do
+              :normal -> :ok
+              :shutdown -> :ok
+              {:shutdown, _} -> :ok
+              _ -> abort("Server crashed: #{inspect(reason)}")
+            end
+        end
+
+      {:error, reason} ->
+        abort("Failed to start server: #{inspect(reason)}")
+    end
   end
 
   defp parse_serve_args(argv) do
@@ -122,7 +129,7 @@ defmodule OrgGarden.CLI do
   def handle_build(argv) do
     quartz_path = require_quartz_env()
     {notes_dir, output_dir, content_dir, _opts} = parse_build_args(argv)
-    pipeline_opts = build_pipeline_opts()
+    pipeline_opts = Config.pipeline_opts()
 
     # Full batch export
     wipe(content_dir)
@@ -130,7 +137,7 @@ defmodule OrgGarden.CLI do
     run_pipeline(content_dir, pipeline_opts)
     generate_index(content_dir)
 
-    node_path = System.get_env("NODE_PATH", "node")
+    node_path = Config.get(:node_path, "node")
 
     IO.puts("==> Building static site with Quartz...")
 
@@ -177,7 +184,7 @@ defmodule OrgGarden.CLI do
 
   def handle_export(argv) do
     {notes_dir, output_dir, content_dir, watch?} = parse_export_args(argv)
-    pipeline_opts = build_pipeline_opts()
+    pipeline_opts = Config.pipeline_opts()
 
     # Phase 1-4: full batch export
     wipe(content_dir)
@@ -197,16 +204,29 @@ defmodule OrgGarden.CLI do
     if watch? do
       IO.puts("==> Watching #{notes_dir} for .org changes... (Ctrl+C to stop)")
 
-      {:ok, _pid} =
-        OrgGarden.Watcher.start_link(
-          notes_dir: notes_dir,
-          output_dir: output_dir,
-          content_dir: content_dir,
-          pipeline_opts: pipeline_opts,
-          transforms: @transforms
+      {:ok, pid} =
+        DynamicSupervisor.start_child(
+          OrgGarden.DynamicSupervisor,
+          {OrgGarden.Watcher,
+           notes_dir: notes_dir,
+           output_dir: output_dir,
+           content_dir: content_dir,
+           pipeline_opts: pipeline_opts,
+           transforms: @transforms}
         )
 
-      Process.sleep(:infinity)
+      # Wait for watcher to exit
+      ref = Process.monitor(pid)
+
+      receive do
+        {:DOWN, ^ref, :process, ^pid, reason} ->
+          case reason do
+            :normal -> :ok
+            :shutdown -> :ok
+            {:shutdown, _} -> :ok
+            _ -> abort("Watcher crashed: #{inspect(reason)}")
+          end
+      end
     end
   end
 
@@ -235,7 +255,7 @@ defmodule OrgGarden.CLI do
           dir
 
         [] ->
-          System.get_env("NOTES_DIR") ||
+          Config.get(:notes_dir) ||
             abort("Usage: org-garden #{command} <notes-dir> [options]")
       end
 
@@ -249,7 +269,7 @@ defmodule OrgGarden.CLI do
   end
 
   defp extract_output_dir(opts) do
-    (opts[:output] || System.get_env("OUTPUT_DIR") || File.cwd!())
+    (opts[:output] || Config.get(:output_dir) || File.cwd!())
     |> Path.expand()
   end
 
@@ -328,7 +348,7 @@ defmodule OrgGarden.CLI do
   # ---------------------------------------------------------------------------
 
   defp require_quartz_env do
-    case System.get_env("QUARTZ_PATH") do
+    case Config.get(:quartz_path) do
       nil ->
         abort("""
         Error: QUARTZ_PATH environment variable not set.
@@ -355,19 +375,6 @@ defmodule OrgGarden.CLI do
     end
   end
 
-  defp build_pipeline_opts do
-    %{
-      zotero_url: System.get_env("ZOTERO_URL", "http://localhost:23119"),
-      bibtex_file: System.get_env("BIBTEX_FILE"),
-      citation_mode:
-        case System.get_env("CITATION_MODE", "warn") do
-          "silent" -> :silent
-          "strict" -> :strict
-          _ -> :warn
-        end
-    }
-  end
-
   defp abort(message) do
     IO.puts(:stderr, message)
     System.halt(1)