feat: redesign SCM workshop handling – remove workshop_item_id requirement, add user ID entry, deprecate steam_workshop menu

- server_content_helpers.php: remove workshop_item_id from required fields/validation; support newline-separated IDs; add scm_validate_workshop_user_ids(); update help text; add new template policy columns to ensure_phase2_schema; add content_id guard to ensure_workshop_schema
- addons_manager.php: rename admin workshop_item_id row to "Default Workshop IDs (Optional)" with updated label
- user_addons.php: route workshop_item type to workshop_content page instead of addons installer
- workshop_content.php: accept addon_id param; show template info; use textarea for multi-ID entry; update heading/help text
- workshop_action.php: accept addon_id param; resolve workshop_app_id from addon template; pass extra_manifest to manifest-and-run; store content_id on insert; use newline/comma-separated IDs
- addons_installer.php: redirect workshop_item addon_type to workshop_content page
- module.php: db_version 6 with allow_user_workshop_ids, max_workshop_ids, required_workshop_ids, blocked_workshop_ids on addons; content_id on server_content_workshop
- server_content_categories.php: rename "Steam Workshop Item" → "Steam Workshop Mods"
- steam_workshop/module.php: empty $module_menus, mark deprecated, bump version to 3.3
- addonsmanager.js: remove #scm-row-workshop-id from steam_workshop admin rows

Agent-Logs-Url: https://github.com/GameServerPanel/GSP/sessions/6a328ac8-2f82-4943-93a9-7660bf42a2fd

Co-authored-by: iaretechnician <2749183+iaretechnician@users.noreply.github.com>

Panel/modules/addonsmanager/addons_manager.php

@@ -198,11 +198,11 @@ function exec_ogp_module() {
 			</tr>
 			<tr id="scm-row-workshop-id">
 				<td align="right">
-					<b><?php print_lang('workshop_id'); ?></b>
+					<b>Default Workshop IDs (Optional)</b>
 				</td>
 				<td align="left">
-					<input type="text" value="<?php echo htmlspecialchars($workshop_item_id, ENT_QUOTES, 'UTF-8'); ?>" name="workshop_item_id" size="85" placeholder="e.g. 450814997" />
-					<small style="color:#666;">Example Arma 3 Workshop ID: 450814997</small>
+					<input type="text" value="<?php echo htmlspecialchars($workshop_item_id, ENT_QUOTES, 'UTF-8'); ?>" name="workshop_item_id" size="85" placeholder="Leave blank – users enter Workshop IDs on their server page" />
+					<small style="color:#666;">Optional. Users enter the actual Workshop IDs they want installed from their own server page. This field is not required.</small>
 				</td>
 			</tr>
 			<tr id="scm-row-workshop-app-id">