feat(web): switch to path-based URL strategy

Remove hash from URLs (/#/login -> /login) using usePathUrlStrategy().
Uses conditional imports to only apply on web, keeping mobile/desktop
builds unaffected.

Required for OIDC callback to work - Authentik redirects to /callback
which Flutter now recognizes as a route.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/core/config/url_strategy.dart

@@ -0,0 +1,5 @@
+/// URL strategy with conditional imports for web/non-web platforms.
+library;
+
+export 'url_strategy_stub.dart'
+    if (dart.library.js_interop) 'url_strategy_web.dart';

lib/core/config/url_strategy_stub.dart

@@ -0,0 +1,4 @@
+/// Stub for non-web platforms - does nothing.
+void configureUrlStrategy() {
+  // No-op on mobile/desktop
+}

lib/core/config/url_strategy_web.dart

@@ -0,0 +1,10 @@
+/// Web-specific URL strategy configuration.
+library;
+
+import 'package:flutter_web_plugins/url_strategy.dart';
+
+void configureUrlStrategy() {
+  // Use path-based URLs instead of hash-based (e.g., /login instead of /#/login)
+  // Required for OIDC callback to work properly
+  usePathUrlStrategy();
+}

lib/main.dart

@@ -4,11 +4,15 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import 'app.dart';
+import 'core/config/url_strategy.dart';
 import 'version.g.dart';
 
 void main() {
   WidgetsFlutterBinding.ensureInitialized();
 
+  // Use path-based URLs on web (no-op on mobile/desktop)
+  configureUrlStrategy();
+
   developer.log(
     '${AppVersion.name} v${AppVersion.fullVersion}',
     name: 'tatlock_ui',