feat(plugins): add i18n API methods and fix LANGUAGE_CHANGE hook

Phase 4-5: Plugin API Extensions and Language Switching

- Add translate(), formatDate(), getCurrentLanguage() to PluginAPI
- Inject PluginI18nService into PluginAPI constructor
- Update PluginRunner to pass PluginI18nService to PluginAPI
- Fix LANGUAGE_CHANGE hook bug (was firing on work context changes)
- Add proper languageChange$ effect listening to global config updates
- Wire language changes to PluginI18nService.setCurrentLanguage()
- Remove incorrect workContextChange$ effect dispatch

Translation API features:
- Simple translate(key, params?) with fallback chain
- Locale-aware formatDate(date, format) with predefined formats
- getCurrentLanguage() to get current app language

Language switching:
- Listens to updateGlobalConfigSection for 'localization' section
- Uses distinctUntilChanged to fire only on actual language changes
- Updates plugin i18n service and dispatches hook to plugins

src/app/plugins/plugin-api.ts

@@ -23,6 +23,8 @@ import {
 } from '@super-productivity/plugin-api';
 import { PluginBridgeService } from './plugin-bridge.service';
 import { PluginLog } from '../core/log';
+import { PluginI18nService } from './plugin-i18n.service';
+import { formatDateForPlugin } from './plugin-i18n-date.util';
 import {
   projectCopyToProjectData,
   projectDataToPartialProjectCopy,
@@ -62,6 +64,7 @@ export class PluginAPI implements PluginAPIInterface {
     public cfg: PluginBaseCfg,
     private _pluginId: string,
     private _pluginBridge: PluginBridgeService,
+    private _pluginI18nService: PluginI18nService,
     private _manifest?: PluginManifest,
   ) {
     // Get bound methods for this plugin
@@ -476,6 +479,33 @@ export class PluginAPI implements PluginAPIInterface {
     return this._pluginBridge.setSimpleCounterDate(id, date, value);
   }
 
+  /**
+   * Translate a key using plugin's translation files
+   * Falls back to English, then to the key itself if not found
+   */
+  translate(key: string, params?: Record<string, string | number>): string {
+    return this._pluginI18nService.translate(this._pluginId, key, params);
+  }
+
+  /**
+   * Format a date according to predefined format and current locale
+   * Supports: 'short', 'medium', 'long', 'time', 'datetime'
+   */
+  formatDate(
+    date: Date | string | number,
+    format: 'short' | 'medium' | 'long' | 'time' | 'datetime',
+  ): string {
+    const locale = this._pluginI18nService.getCurrentLanguage();
+    return formatDateForPlugin(date, format, locale);
+  }
+
+  /**
+   * Get the current app language code
+   */
+  getCurrentLanguage(): string {
+    return this._pluginI18nService.getCurrentLanguage();
+  }
+
   /**
    * Clean up all resources associated with this plugin API instance
    * Called when the plugin is being unloaded

src/app/plugins/plugin-hooks.effects.ts

@@ -1,7 +1,15 @@
 import { inject, Injectable } from '@angular/core';
 import { createEffect, ofType } from '@ngrx/effects';
 import { select, Store } from '@ngrx/store';
-import { filter, map, switchMap, take, tap, withLatestFrom } from 'rxjs/operators';
+import {
+  distinctUntilChanged,
+  filter,
+  map,
+  switchMap,
+  take,
+  tap,
+  withLatestFrom,
+} from 'rxjs/operators';
 import { EMPTY } from 'rxjs';
 
 import {
@@ -9,10 +17,12 @@ import {
   selectTaskFeatureState,
 } from '../features/tasks/store/task.selectors';
 import { selectProjectFeatureState } from '../features/project/store/project.selectors';
+import { selectLocalizationConfig } from '../features/config/store/global-config.reducer';
+import { updateGlobalConfigSection } from '../features/config/store/global-config.actions';
 import { Task } from '../features/tasks/task.model';
 import { PluginService } from './plugin.service';
 import { PluginHooks } from './plugin-api.model';
-import { setActiveWorkContext } from '../features/work-context/store/work-context.actions';
+import { PluginI18nService } from './plugin-i18n.service';
 import { TaskSharedActions } from '../root-store/meta/task-shared.actions';
 import {
   setCurrentTask,
@@ -41,6 +51,7 @@ export class PluginHooksEffects {
   private readonly actions$ = inject(LOCAL_ACTIONS);
   private readonly store = inject(Store);
   private readonly pluginService = inject(PluginService);
+  private readonly pluginI18nService = inject(PluginI18nService);
 
   taskComplete$ = createEffect(
     () =>
@@ -191,14 +202,22 @@ export class PluginHooksEffects {
     { dispatch: false },
   );
 
-  workContextChange$ = createEffect(
+  // Language change effect - listens to actual language config changes
+  languageChange$ = createEffect(
     () =>
       this.actions$.pipe(
-        ofType(setActiveWorkContext),
-        tap((action) => {
+        ofType(updateGlobalConfigSection),
+        filter((action) => action.sectionKey === 'localization'),
+        withLatestFrom(this.store.pipe(select(selectLocalizationConfig))),
+        map(([_, localizationConfig]) => localizationConfig.lng),
+        distinctUntilChanged(),
+        tap((newLanguage) => {
+          // Update plugin i18n service with new language
+          this.pluginI18nService.setCurrentLanguage(newLanguage);
+
+          // Dispatch hook to notify plugins
           this.pluginService.dispatchHook(PluginHooks.LANGUAGE_CHANGE, {
-            activeId: action.activeId,
-            activeType: action.activeType,
+            newLanguage,
           });
         }),
       ),

src/app/plugins/plugin-runner.ts

@@ -3,6 +3,7 @@ import { PluginManifest, PluginBaseCfg, PluginInstance } from './plugin-api.mode
 import { PluginAPI } from './plugin-api';
 import { PluginBridgeService } from './plugin-bridge.service';
 import { PluginSecurityService } from './plugin-security';
+import { PluginI18nService } from './plugin-i18n.service';
 import { SnackService } from '../core/snack/snack.service';
 import { PluginCleanupService } from './plugin-cleanup.service';
 import { PluginLog } from '../core/log';
@@ -17,6 +18,7 @@ import { PluginLog } from '../core/log';
 export class PluginRunner {
   private _pluginBridge = inject(PluginBridgeService);
   private _securityService = inject(PluginSecurityService);
+  private _pluginI18nService = inject(PluginI18nService);
   private _snackService = inject(SnackService);
   private _cleanupService = inject(PluginCleanupService);
 
@@ -34,7 +36,13 @@ export class PluginRunner {
   ): Promise<PluginInstance> {
     try {
       // Create plugin API
-      const pluginAPI = new PluginAPI(baseCfg, manifest.id, this._pluginBridge, manifest);
+      const pluginAPI = new PluginAPI(
+        baseCfg,
+        manifest.id,
+        this._pluginBridge,
+        this._pluginI18nService,
+        manifest,
+      );
 
       // executeNodeScript is now automatically bound if permitted via createBoundMethods