feat: Integrate HTML templates with FastAPI

- Created template_helpers.py for centralized template rendering
- Added ux_features.css for enhanced UX styling
- Implemented JavaScript modules for:
  - Keyboard shortcuts (Ctrl+K, Ctrl+R navigation)
  - User preferences persistence
  - Undo/redo functionality (Ctrl+Z/Ctrl+Y)
  - Mobile responsive features
  - Touch gesture support
  - Accessibility features (ARIA, focus management)
  - Screen reader support
  - Color contrast compliance (WCAG)
  - Multi-screen support
- Updated page_controller.py and error_controller.py to use template helpers
- Created comprehensive template integration tests
- All templates verified: index.html, login.html, setup.html, queue.html, error.html
- Maintained responsive layout and theme switching
- Updated instructions.md (removed completed task)
- Updated infrastructure.md with template integration details

src/server/controllers/error_controller.py

@@ -6,7 +6,7 @@ This module provides custom error handlers for different HTTP status codes.
 from fastapi import HTTPException, Request
 from fastapi.responses import JSONResponse
 
-from src.server.utils.templates import templates
+from src.server.utils.template_helpers import render_template
 
 
 async def not_found_handler(request: Request, exc: HTTPException):
@@ -16,9 +16,11 @@ async def not_found_handler(request: Request, exc: HTTPException):
             status_code=404,
             content={"detail": "API endpoint not found"}
         )
-    return templates.TemplateResponse(
+    return render_template(
         "error.html",
-        {"request": request, "error": "Page not found", "status_code": 404}
+        request,
+        context={"error": "Page not found", "status_code": 404},
+        title="404 - Not Found"
     )
 
 
@@ -29,11 +31,9 @@ async def server_error_handler(request: Request, exc: Exception):
             status_code=500,
             content={"detail": "Internal server error"}
         )
-    return templates.TemplateResponse(
+    return render_template(
         "error.html",
-        {
-            "request": request,
-            "error": "Internal server error",
-            "status_code": 500
-        }
-    )
+        request,
+        context={"error": "Internal server error", "status_code": 500},
+        title="500 - Server Error"
+    )