perf(bundle): lazy-load the nunjucks template engine (#2535)

Closes #2531.

## Summary

The full `nunjucks` templating engine (~226KB) plus `ha-nunjucks`
(~46KB) — roughly **272KB, ~13% of the eager entry chunk** — was
statically imported and downloaded by every card on initial load, even
though templates only apply when a config value contains a `{{ … }}` /
`{% … %}` delimiter. Most cards use no templates and never need the
engine.

This defers the engine behind a dynamic `import('ha-nunjucks/dist')` so
it ships in a separate, on-demand chunk instead of the eager
`card-*.js`.

## Approach

The render path (`TemplateRenderer.renderRecursively`) is **kept
synchronous** — it is called from many synchronous hot paths
(condition/trigger evaluators, picture-elements rendering, actions,
folder matchers), and making it async would be a large, high-risk
refactor of the evaluation core.

Instead:

- **New `src/card-controller/templates/engine.ts`** — a module-level
singleton lazy loader (`loadTemplateEngine()` / `getTemplateEngine()`)
shared across all `TemplateRenderer` instances, plus a
`containsTemplate()` delimiter helper.
- **Delimiter gating** — strings without a delimiter never touch the
engine (the overwhelming majority of renders).
- **Pre-warm at config time** — because every template string originates
in the config, a new mandatory `TEMPLATE_ENGINE` initialization aspect
loads the engine before first render whenever the config contains a
delimiter. This **guarantees no raw `{{ … }}` flash**: content/condition
rendering is blocked until the engine is present for template-using
cards. Cards without templates never load it.

## Result

- nunjucks + ha-nunjucks move out of the eager chunk into a separate
chunk fetched only when a card actually uses templates.
- No change to the synchronous public render API; condition/trigger
evaluation core untouched.

## Tests

- New `engine.ts` loader coverage (concurrent load, cached reuse,
not-loaded fallback).
- The 11 existing test files that render real (delimiter-bearing)
templates declare their dependency explicitly via
`beforeAll(loadTemplateEngine)` — no global/implicit setup hook.
- Full suite green (4764 tests), lint and ts-prune clean, per-file 100%
coverage maintained for the affected directories.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_016ykWemdkZrgywvC71pHc6c

---
_Generated by [Claude
Code](https://claude.ai/code/session_016ykWemdkZrgywvC71pHc6c)_

src/card.ts

@@ -43,6 +43,7 @@ import './components/status-bar';
 import './components/thumbnail-carousel.js';
 import './components/views.js';
 
+import type { TemplateRendererGetEvent } from './card-controller/templates/renderer-via-event.js';
 import type { AdvancedCameraCardViews } from './components/views.js';
 import type { ConditionStateManagerGetEvent } from './condition-trigger/conditions/state-manager-via-event.js';
 import type { StatusBarItem } from './config/schema/actions/types.js';
@@ -483,14 +484,20 @@ class AdvancedCameraCard extends LitElement {
             ${fullCardIssue ? renderNotificationBlock(fullCardIssue.notification) : ''}
           </div>
           ${this._renderMenuStatusContainer('bottom')}
-          ${this._config?.elements
+          ${this._config?.elements &&
+          this._controller.getInitializationManager().isInitializedMandatory()
             ? // Elements need to render after the main views so it can render 'on
-              // top'.
+              // top'. They are held until the card is initialized: the template
+              // renderer loads lazily as a mandatory init aspect (when the
+              // config uses templates), so rendering elements earlier could
+              // emit raw, unrendered templates or evaluate their visibility
+              // conditions before the renderer is available.
               html` <advanced-camera-card-elements
                 ${ref(this._refElements)}
                 .hass=${this._hass}
                 .elements=${this._config?.elements}
                 .conditionStateManager=${this._controller.getConditionStateManager()}
+                .templateRenderer=${this._controller.getTemplateManager()}
                 @advanced-camera-card:menu:add=${(ev: CustomEvent<MenuItem>) => {
                   this._menuButtonController.addDynamicMenuButton(ev.detail);
                   this.requestUpdate();
@@ -518,6 +525,11 @@ class AdvancedCameraCard extends LitElement {
                 ) => {
                   ev.conditionStateManager = this._controller.getConditionStateManager();
                 }}
+                @advanced-camera-card:template-renderer:get=${(
+                  ev: TemplateRendererGetEvent,
+                ) => {
+                  ev.templateRenderer = this._controller.getTemplateManager();
+                }}
               >
               </advanced-camera-card-elements>`
             : ``}