Add build timestamp to footer with shared time formatting helpers

- Add compile-time @build_timestamp to Application module
- Create ToweropsWeb.TimeHelpers module for shared time formatting
- Update footer to display 'Last deployed Xm ago · YYYY-MM-DD HH:MM:SS UTC'
- Refactor AgentLive.Helpers to delegate to shared TimeHelpers
- Consolidate duplicate time formatting logic into single module
- Timestamp updates automatically on each build/deploy

lib/towerops/application.ex

@@ -5,6 +5,9 @@ defmodule Towerops.Application do
 
   use Application
 
+  # Capture the build/deploy timestamp at compile time
+  @build_timestamp DateTime.utc_now()
+
   @impl true
   def start(_type, _args) do
     # Run migrations on startup (Ecto handles locking for concurrent runs)
@@ -44,4 +47,13 @@ defmodule Towerops.Application do
     ToweropsWeb.Endpoint.config_change(changed, removed)
     :ok
   end
+
+  @doc """
+  Returns the build/deploy timestamp.
+
+  This timestamp is captured at compile time and represents when the
+  application was last built/deployed.
+  """
+  @spec build_timestamp() :: DateTime.t()
+  def build_timestamp, do: @build_timestamp
 end

lib/towerops_web/components/layouts.ex

@@ -411,15 +411,28 @@ defmodule ToweropsWeb.Layouts do
   end
 
   @doc """
-  Renders the application footer with copyright notice.
+  Renders the application footer with copyright notice and deploy timestamp.
   """
   def footer(assigns) do
+    alias ToweropsWeb.TimeHelpers
+
+    build_time = Towerops.Application.build_timestamp()
+
+    assigns =
+      assigns
+      |> assign(:build_time, build_time)
+      |> assign(:time_ago, TimeHelpers.format_time_ago(build_time))
+      |> assign(:formatted_time, TimeHelpers.format_iso8601(build_time))
+
     ~H"""
     <footer class="border-t border-zinc-200 bg-white dark:border-zinc-800 dark:bg-zinc-900">
       <div class="mx-auto max-w-7xl px-4 py-6 sm:px-6 lg:px-8">
-        <p class="text-center text-sm text-zinc-600 dark:text-zinc-400">
-          Copyright © {Date.utc_today().year} Towerops
-        </p>
+        <div class="flex flex-col items-center gap-2 text-sm text-zinc-600 dark:text-zinc-400">
+          <p>Copyright © {Date.utc_today().year} Towerops</p>
+          <p class="text-xs">
+            Last deployed {@time_ago} · {@formatted_time}
+          </p>
+        </div>
       </div>
     </footer>
     """

lib/towerops_web/helpers/time_helpers.ex

@@ -0,0 +1,106 @@
+defmodule ToweropsWeb.TimeHelpers do
+  @moduledoc """
+  Helper functions for formatting time and date values.
+  """
+
+  @doc """
+  Formats a DateTime into a human-readable "time ago" string.
+
+  Supports short time periods (seconds, minutes, hours, days) and
+  long time periods (months, years) for things like build timestamps.
+
+  ## Examples
+
+      iex> datetime = DateTime.add(DateTime.utc_now(), -65, :second)
+      iex> ToweropsWeb.TimeHelpers.format_time_ago(datetime)
+      "1m ago"
+
+      iex> datetime = DateTime.add(DateTime.utc_now(), -7200, :second)
+      iex> ToweropsWeb.TimeHelpers.format_time_ago(datetime)
+      "2h ago"
+
+  """
+  @spec format_time_ago(DateTime.t() | nil) :: String.t()
+  def format_time_ago(nil), do: "Never"
+
+  def format_time_ago(datetime) do
+    now = DateTime.utc_now()
+    diff = DateTime.diff(now, datetime, :second)
+
+    cond do
+      diff < 60 ->
+        "#{diff}s ago"
+
+      diff < 3600 ->
+        minutes = div(diff, 60)
+        "#{minutes}m ago"
+
+      diff < 86_400 ->
+        hours = div(diff, 3600)
+        "#{hours}h ago"
+
+      diff < 2_592_000 ->
+        days = div(diff, 86_400)
+        "#{days}d ago"
+
+      diff < 31_536_000 ->
+        months = div(diff, 2_592_000)
+        "#{months}mo ago"
+
+      true ->
+        years = div(diff, 31_536_000)
+        "#{years}y ago"
+    end
+  end
+
+  @doc """
+  Formats a DateTime into a full date and time string.
+
+  ## Examples
+
+      iex> datetime = ~U[2026-01-15 14:34:00Z]
+      iex> ToweropsWeb.TimeHelpers.format_datetime(datetime)
+      "Jan 15, 2026 at 02:34 PM UTC"
+
+  """
+  @spec format_datetime(DateTime.t() | nil) :: String.t()
+  def format_datetime(nil), do: "Never"
+
+  def format_datetime(datetime) do
+    Calendar.strftime(datetime, "%b %d, %Y at %I:%M %p %Z")
+  end
+
+  @doc """
+  Formats a DateTime into a short date string.
+
+  ## Examples
+
+      iex> datetime = ~U[2026-01-15 14:34:00Z]
+      iex> ToweropsWeb.TimeHelpers.format_date(datetime)
+      "Jan 15, 2026"
+
+  """
+  @spec format_date(DateTime.t() | nil) :: String.t()
+  def format_date(nil), do: "Never"
+
+  def format_date(datetime) do
+    Calendar.strftime(datetime, "%b %d, %Y")
+  end
+
+  @doc """
+  Formats a DateTime into ISO 8601 format with UTC timezone.
+
+  ## Examples
+
+      iex> datetime = ~U[2026-01-15 14:34:00Z]
+      iex> ToweropsWeb.TimeHelpers.format_iso8601(datetime)
+      "2026-01-15 14:34:00 UTC"
+
+  """
+  @spec format_iso8601(DateTime.t() | nil) :: String.t()
+  def format_iso8601(nil), do: "Never"
+
+  def format_iso8601(datetime) do
+    Calendar.strftime(datetime, "%Y-%m-%d %H:%M:%S UTC")
+  end
+end

lib/towerops_web/live/agent_live/helpers.ex

@@ -57,19 +57,10 @@ defmodule ToweropsWeb.AgentLive.Helpers do
   Formats a DateTime into a human-readable "time ago" string.
 
   Returns strings like "5s ago", "3m ago", "2h ago", or "5d ago".
+
+  Delegates to ToweropsWeb.TimeHelpers.format_time_ago/1.
   """
-  def format_last_seen(nil), do: "Never"
-
-  def format_last_seen(datetime) do
-    seconds_ago = DateTime.diff(DateTime.utc_now(), datetime, :second)
-
-    cond do
-      seconds_ago < 60 -> "#{seconds_ago}s ago"
-      seconds_ago < 3600 -> "#{div(seconds_ago, 60)}m ago"
-      seconds_ago < 86_400 -> "#{div(seconds_ago, 3600)}h ago"
-      true -> "#{div(seconds_ago, 86_400)}d ago"
-    end
-  end
+  defdelegate format_last_seen(datetime), to: ToweropsWeb.TimeHelpers, as: :format_time_ago
 
   @doc """
   Formats uptime in seconds to a human-readable string.
@@ -94,23 +85,19 @@ defmodule ToweropsWeb.AgentLive.Helpers do
   Formats a DateTime into a full date and time string.
 
   Returns strings like "Jan 15, 2026 at 2:34 PM UTC".
-  """
-  def format_datetime(nil), do: "Never"
 
-  def format_datetime(datetime) do
-    Calendar.strftime(datetime, "%b %d, %Y at %I:%M %p %Z")
-  end
+  Delegates to ToweropsWeb.TimeHelpers.format_datetime/1.
+  """
+  defdelegate format_datetime(datetime), to: ToweropsWeb.TimeHelpers
 
   @doc """
   Formats a DateTime into a short date string.
 
   Returns strings like "Jan 15, 2026".
-  """
-  def format_date(nil), do: "Never"
 
-  def format_date(datetime) do
-    Calendar.strftime(datetime, "%b %d, %Y")
-  end
+  Delegates to ToweropsWeb.TimeHelpers.format_date/1.
+  """
+  defdelegate format_date(datetime), to: ToweropsWeb.TimeHelpers
 
   @doc """
   Formats a DateTime into a relative time with full datetime in parentheses.