feat: process pending transactions from lunchflow (#731)

* feat(config): add Lunchflow runtime configuration flags

* feat(api): add include_pending parameter to Lunchflow API

* feat(processor): add pending metadata support to Lunchflow processor

* feat(processor): generate temporary IDs for pending transactions

* feat(importer): integrate pending transaction support in sync

* fix(importer): improve deduplication for transactions without IDs

* feat(model): add Lunchflow pending support to Transaction scopes

* test: add Lunchflow processor pending metadata tests

* docs: update AGENTS.md for Lunchflow pending support

* chore: remove unused variable

* fix: simplify key check

* fix: dotenv-linter key order

* fix: avoid collapsing distinct pending transactions

* fix: prevent unbounded raw payload growth for blank IDs

app/models/concerns/lunchflow_transaction_hash.rb

@@ -0,0 +1,28 @@
+# Shared concern for generating content-based hashes for Lunchflow transactions
+# Used by both the importer (for deduplication) and processor (for temporary external IDs)
+module LunchflowTransactionHash
+  extend ActiveSupport::Concern
+
+  private
+
+    # Generate a content-based hash for a transaction
+    # This creates a deterministic identifier based on transaction attributes
+    # Used for:
+    # - Deduplicating blank-ID transactions in the importer
+    # - Generating temporary external IDs in the processor
+    #
+    # @param tx [Hash] Transaction data with indifferent access
+    # @return [String] MD5 hash of transaction attributes
+    def content_hash_for_transaction(tx)
+      attributes = [
+        tx[:accountId],
+        tx[:amount],
+        tx[:currency],
+        tx[:date],
+        tx[:merchant],
+        tx[:description]
+      ].compact.join("|")
+
+      Digest::MD5.hexdigest(attributes)
+    end
+end