Fix httpx.Timeout configuration in PyPI proxy

- Add POST /api/v1/cache/resolve endpoint that caches artifacts by package
  coordinates (source_type, package, version) instead of requiring a URL
- Server finds download URL from configured upstream sources (PyPI supported)
- Reduces footer padding from 24px to 12px for cleaner layout

backend/app/pypi_proxy.py

@@ -156,10 +156,7 @@ async def pypi_simple_index(
 
             simple_url = source.url.rstrip('/') + '/simple/'
 
-            timeout = httpx.Timeout(
+            timeout = httpx.Timeout(PROXY_READ_TIMEOUT, connect=PROXY_CONNECT_TIMEOUT)
-                connect=PROXY_CONNECT_TIMEOUT,
-                read=PROXY_READ_TIMEOUT,
-            )
 
             with httpx.Client(timeout=timeout, follow_redirects=False) as client:
                 response = client.get(
@@ -247,10 +244,7 @@ async def pypi_package_versions(
 
             package_url = source.url.rstrip('/') + f'/simple/{normalized_name}/'
 
-            timeout = httpx.Timeout(
+            timeout = httpx.Timeout(PROXY_READ_TIMEOUT, connect=PROXY_CONNECT_TIMEOUT)
-                connect=PROXY_CONNECT_TIMEOUT,
-                read=PROXY_READ_TIMEOUT,
-            )
 
             with httpx.Client(timeout=timeout, follow_redirects=False) as client:
                 response = client.get(
@@ -385,10 +379,7 @@ async def pypi_download_file(
             headers.update(_build_auth_headers(matched_source))
         auth = _get_basic_auth(matched_source) if matched_source else None
 
-        timeout = httpx.Timeout(
+        timeout = httpx.Timeout(300.0, connect=PROXY_CONNECT_TIMEOUT)  # 5 minutes for large files
-            connect=PROXY_CONNECT_TIMEOUT,
-            read=300.0,  # 5 minutes for large files
-        )
 
         # Fetch the file
         logger.info(f"PyPI proxy: fetching {filename} from {upstream_url}")