feat(frontend): T44 setup FastAPI static files and templates

- Mount static files on /static endpoint
- Configure Jinja2Templates with directory structure
- Create base template with Pico.css, HTMX, Chart.js
- Create all template subdirectories (auth, dashboard, keys, tokens, profile, components)
- Create initial CSS and JS files
- Add tests for static files and templates configuration

Tests: 12 passing
Coverage: 100% on new configuration code

src/openrouter_monitor/main.py

@@ -3,9 +3,12 @@
 Main application entry point for OpenRouter API Key Monitor.
 """
 from contextlib import asynccontextmanager
+from pathlib import Path
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.staticfiles import StaticFiles
+from fastapi.templating import Jinja2Templates
 
 from openrouter_monitor.config import get_settings
 from openrouter_monitor.routers import api_keys
@@ -32,6 +35,12 @@ async def lifespan(app: FastAPI):
     shutdown_scheduler()
 
 
+# Get project root directory
+PROJECT_ROOT = Path(__file__).parent.parent.parent
+
+# Configure Jinja2 templates
+templates = Jinja2Templates(directory=str(PROJECT_ROOT / "templates"))
+
 # Create FastAPI app
 app = FastAPI(
     title="OpenRouter API Key Monitor",
@@ -41,6 +50,9 @@ app = FastAPI(
     lifespan=lifespan,
 )
 
+# Mount static files
+app.mount("/static", StaticFiles(directory=str(PROJECT_ROOT / "static")), name="static")
+
 # CORS middleware
 app.add_middleware(
     CORSMiddleware,