feat: add frontend logging system with router and visibility tracking

src/app/core/services/theme.service.ts

@@ -1,10 +1,12 @@
 import { DOCUMENT } from '@angular/common';
-import { DestroyRef, Inject, Injectable, effect, signal, computed } from '@angular/core';
+import { DestroyRef, Inject, Injectable, effect, signal, computed, inject } from '@angular/core';
+import { LogService } from '../../../core/logging/log.service';
 
 export type ThemeName = 'light' | 'dark';
 
 @Injectable({ providedIn: 'root' })
 export class ThemeService {
+  private readonly logService = inject(LogService);
   private static readonly STORAGE_KEY = 'obsiwatcher.theme';
 
   private readonly document = this.doc;
@@ -50,11 +52,30 @@ export class ThemeService {
   }
 
   setTheme(theme: ThemeName): void {
+    const previousTheme = this.currentTheme();
     this.currentTheme.set(theme);
+    
+    // Log theme change
+    if (previousTheme !== theme) {
+      this.logService.log('THEME_CHANGE', {
+        from: previousTheme,
+        to: theme,
+      });
+    }
   }
 
   toggleTheme(): void {
+    const previousTheme = this.currentTheme();
     this.currentTheme.update(theme => (theme === 'light' ? 'dark' : 'light'));
+    
+    // Log theme change
+    const newTheme = this.currentTheme();
+    if (previousTheme !== newTheme) {
+      this.logService.log('THEME_CHANGE', {
+        from: previousTheme,
+        to: newTheme,
+      });
+    }
   }
 
   private detectSystemTheme(): ThemeName {

src/app/graph/graph-settings.service.ts

@@ -1,7 +1,8 @@
-import { Injectable, signal } from '@angular/core';
+import { Injectable, signal, inject } from '@angular/core';
 import { HttpClient } from '@angular/common/http';
 import { BehaviorSubject, Subject, debounceTime, catchError, of, tap } from 'rxjs';
 import { GraphConfig, DEFAULT_GRAPH_CONFIG, validateGraphConfig } from './graph-settings.types';
+import { LogService } from '../../core/logging/log.service';
 
 /** Response from graph config API */
 interface GraphConfigResponse {
@@ -20,6 +21,7 @@ export type Unsubscribe = () => void;
   providedIn: 'root'
 })
 export class GraphSettingsService {
+  private readonly logService = inject(LogService);
   private configSubject = new BehaviorSubject<GraphConfig>(DEFAULT_GRAPH_CONFIG);
   private saveQueue = new Subject<Partial<GraphConfig>>();
   private currentRev: string | null = null;
@@ -85,6 +87,11 @@ export class GraphSettingsService {
 
     // Queue for debounced save
     this.saveQueue.next(patch);
+    
+    // Log settings change
+    this.logService.log('GRAPH_VIEW_SETTINGS_CHANGE', {
+      changes: Object.keys(patch),
+    });
   }
 
   /**