Initial implementation of the reconciliation script

Standalone Ruby script reconciling GoCardless payments, Dolibarr
invoices (via API), and Shine bank statements. Three-pass engine:
GC↔Dolibarr matching, open invoice audit, payout↔bank verification.
Includes dry-run and --fix mode to auto-mark Dolibarr invoices as paid.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/dolibarr/client.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require "httparty"
+require "json"
+
+module Dolibarr
+  class Client
+    include HTTParty
+
+    class NotFoundError < StandardError; end
+    class ValidationError < StandardError; end
+    class Error < StandardError; end
+
+    def initialize(
+      base_url: ENV.fetch("DOLIBARR_URL"),
+      api_key:  ENV.fetch("DOLIBARR_API_KEY")
+    )
+      @base_url = base_url
+      @headers  = {
+        "DOLAPIKEY"    => api_key,
+        "Content-Type" => "application/json",
+        "Accept"       => "application/json"
+      }
+    end
+
+    def get(path, params = {})
+      perform_request(:get, path, params)
+    end
+
+    def post(path, data = {})
+      perform_request(:post, path, data)
+    end
+
+    def put(path, data = {})
+      perform_request(:put, path, data)
+    end
+
+    private
+
+    def perform_request(method, path, data = {})
+      url = "#{@base_url}#{path}"
+      opts = { headers: @headers }
+
+      case method
+      when :get
+        opts[:query] = data unless data.empty?
+        response = self.class.get(url, opts)
+      when :post
+        opts[:body] = data.to_json
+        response = self.class.post(url, opts)
+      when :put
+        opts[:body] = data.to_json
+        response = self.class.put(url, opts)
+      end
+
+      handle_response(response)
+    rescue => e
+      raise Error, "Connection error: #{e.message}"
+    end
+
+    def handle_response(response)
+      return nil if response.body.nil? || response.body.strip.empty?
+
+      code = response.code.to_i
+      case code
+      when 200..299
+        response.parsed_response
+      when 404
+        raise NotFoundError, "Not found (404)"
+      when 400
+        raise ValidationError, "Validation error: #{response.body}"
+      when 401
+        raise Error, "Authentication failed (401) — check DOLIBARR_API_KEY"
+      when 500..599
+        raise Error, "Dolibarr server error (#{code}): #{response.body}"
+      else
+        raise Error, "Unexpected status #{code}: #{response.body}"
+      end
+    rescue JSON::ParserError => e
+      raise Error, "JSON parse error: #{e.message}"
+    end
+  end
+end