fix: set prebuilds lifecycle parameters on creation and claim (#19252)

## Description

This PR ensures that prebuilt workspaces are properly excluded from the
lifecycle executor and treated as a separate class of workspaces, fully
managed by the prebuild reconciliation loop.

It introduces two lifecycle guarantees:
* When a prebuilt workspace is created (i.e., when the workspace build
completes), all lifecycle-related fields are unset, ensuring the
workspace does not participate in TTL, autostop, autostart, dormancy, or
auto-deletion logic.
* When a prebuilt workspace is claimed, it transitions into a regular
user workspace. At this point, all lifecycle fields are correctly
populated according to template-level configurations, allowing the
workspace to be managed by the lifecycle executor as expected.

## Changes

* Prebuilt workspaces now have all lifecycle-relevant fields unset
during creation
* When a prebuild is claimed:
* Lifecycle fields are set based on template and workspace level
configurations. This ensures a clean transition into the standard
workspace lifecycle flow.
* Updated lifecycle-related SQL update queries to explicitly exclude
prebuilt workspaces.

## Relates 

Related issue: https://github.com/coder/coder/issues/18898

To reduce the scope of this PR and make the review process more
manageable, the original implementation has been split into the
following focused PRs:
* https://github.com/coder/coder/pull/19259
* https://github.com/coder/coder/pull/19263
* https://github.com/coder/coder/pull/19264
* https://github.com/coder/coder/pull/19265

These PRs should be considered in conjunction with this one to
understand the complete set of lifecycle separation changes for prebuilt
workspaces.

coderd/database/queries/prebuilds.sql

@@ -2,7 +2,20 @@
 UPDATE workspaces w
 SET owner_id   = @new_user_id::uuid,
 	name       = @new_name::text,
-	updated_at = NOW()
+	updated_at = @now::timestamptz,
+	-- Update autostart_schedule, next_start_at and ttl according to template and workspace-level
+	-- configurations, allowing the workspace to be managed by the lifecycle executor as expected.
+	autostart_schedule = @autostart_schedule,
+	next_start_at = @next_start_at,
+	ttl = @workspace_ttl,
+	-- Update last_used_at during claim to ensure the claimed workspace is treated as recently used.
+	-- This avoids unintended dormancy caused by prebuilds having stale usage timestamps.
+	last_used_at = @now::timestamptz,
+	-- Clear dormant and deletion timestamps as a safeguard to ensure a clean lifecycle state after claim.
+	-- These fields should not be set on prebuilds, but we defensively reset them here to prevent
+	-- accidental dormancy or deletion by the lifecycle executor.
+	dormant_at = NULL,
+	deleting_at = NULL
 WHERE w.id IN (
 	SELECT p.id
 	FROM workspace_prebuilds p