feat: time based automation (#15022)

## Description

Add automations that trigger based on how long a conversation has been
in a given state.

## Type of change

- [ ] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

- UI flows 
- Specs (https://github.com/chatwoot/chatwoot/pull/15021) 

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sony Mathew <sony@chatwoot.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

db/migrate/20260709060000_add_execution_delay_to_automation_rules.rb

@@ -0,0 +1,5 @@
+class AddExecutionDelayToAutomationRules < ActiveRecord::Migration[7.0]
+  def change
+    add_column :automation_rules, :execution_delay, :integer
+  end
+end

db/migrate/20260709060100_add_status_changed_at_to_conversations.rb

@@ -0,0 +1,5 @@
+class AddStatusChangedAtToConversations < ActiveRecord::Migration[7.0]
+  def change
+    add_column :conversations, :status_changed_at, :datetime
+  end
+end

db/migrate/20260709060200_create_automation_rule_pending_executions.rb

@@ -0,0 +1,21 @@
+class CreateAutomationRulePendingExecutions < ActiveRecord::Migration[7.0]
+  def change
+    create_table :automation_rule_pending_executions do |t|
+      t.references :automation_rule, null: false
+      t.references :conversation, null: false
+      t.references :account, null: false
+      t.bigint :message_id
+      t.datetime :due_at, null: false
+      t.string :episode_key, null: false
+      t.integer :status, null: false, default: 0
+      t.string :skip_reason
+
+      t.timestamps
+    end
+
+    add_index :automation_rule_pending_executions, [:status, :due_at]
+    add_index :automation_rule_pending_executions,
+              [:automation_rule_id, :conversation_id, :episode_key],
+              unique: true, name: 'uniq_automation_pending_execution_episode'
+  end
+end

db/migrate/20260729051500_add_status_updated_at_index_to_automation_rule_pending_executions.rb

@@ -0,0 +1,8 @@
+class AddStatusUpdatedAtIndexToAutomationRulePendingExecutions < ActiveRecord::Migration[7.0]
+  def change
+    # Stale reclaim, the abandoned-row alarm and the terminal purge all filter on status + updated_at;
+    # the (status, due_at) index does not serve them, and terminal rows linger for 30 days.
+    add_index :automation_rule_pending_executions, [:status, :updated_at],
+              name: 'index_automation_pending_executions_on_status_and_updated_at'
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2026_07_28_000001) do
+ActiveRecord::Schema[7.1].define(version: 2026_07_29_051500) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -278,6 +278,25 @@ ActiveRecord::Schema[7.1].define(version: 2026_07_28_000001) do
     t.index ["user_id", "user_type"], name: "user_index"
   end
 
+  create_table "automation_rule_pending_executions", force: :cascade do |t|
+    t.bigint "automation_rule_id", null: false
+    t.bigint "conversation_id", null: false
+    t.bigint "account_id", null: false
+    t.bigint "message_id"
+    t.datetime "due_at", null: false
+    t.string "episode_key", null: false
+    t.integer "status", default: 0, null: false
+    t.string "skip_reason"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id"], name: "index_automation_rule_pending_executions_on_account_id"
+    t.index ["automation_rule_id", "conversation_id", "episode_key"], name: "uniq_automation_pending_execution_episode", unique: true
+    t.index ["automation_rule_id"], name: "index_automation_rule_pending_executions_on_automation_rule_id"
+    t.index ["conversation_id"], name: "index_automation_rule_pending_executions_on_conversation_id"
+    t.index ["status", "due_at"], name: "index_automation_rule_pending_executions_on_status_and_due_at"
+    t.index ["status", "updated_at"], name: "index_automation_pending_executions_on_status_and_updated_at"
+  end
+
   create_table "automation_rules", force: :cascade do |t|
     t.bigint "account_id", null: false
     t.string "name", null: false
@@ -288,6 +307,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_07_28_000001) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.boolean "active", default: true, null: false
+    t.integer "execution_delay"
     t.index ["account_id"], name: "index_automation_rules_on_account_id"
   end
 
@@ -794,6 +814,7 @@ ActiveRecord::Schema[7.1].define(version: 2026_07_28_000001) do
     t.datetime "waiting_since"
     t.text "cached_label_list"
     t.bigint "assignee_agent_bot_id"
+    t.datetime "status_changed_at"
     t.index ["account_id", "display_id"], name: "index_conversations_on_account_id_and_display_id", unique: true
     t.index ["account_id", "id"], name: "index_conversations_on_id_and_account_id"
     t.index ["account_id", "inbox_id", "status", "assignee_id"], name: "conv_acid_inbid_stat_asgnid_idx"