feat: add cookie-persisting HttpSession

HTTP client that persists cookies across requests via
http.cookiejar, for sites requiring login followed by
cookie-authenticated fetches. Supports GET with query params,
form-encoded POST, default/per-request header merging, and
HTTPError-to-response conversion.

src/byteb4rb1e/utils/http/client.py

@@ -6,6 +6,7 @@ GitHub, Bitbucket, etc. are handled by higher-level modules.
 """
 
 from dataclasses import dataclass
+import http.cookiejar
 import json
 import time
 from typing import Any, Dict, Optional
@@ -29,6 +30,93 @@ class HttpResponse:
         return self.data.decode("utf-8", errors="replace")
 
 
+class HttpSession:
+    """HTTP client that persists cookies across requests.
+
+    Suitable for sites that require login followed by
+    cookie-authenticated page fetches.
+    """
+
+    def __init__(
+        self,
+        default_headers: dict[str, str] | None = None,
+        timeout: int = 30,
+    ) -> None:
+        self._timeout = timeout
+        self._default_headers = default_headers or {}
+        self._jar = http.cookiejar.CookieJar()
+        self._opener = urllib.request.build_opener(
+            urllib.request.HTTPCookieProcessor(self._jar),
+        )
+
+    def get(
+        self,
+        url: str,
+        params: dict[str, str] | None = None,
+        headers: dict[str, str] | None = None,
+    ) -> HttpResponse:
+        if params:
+            query = urllib.parse.urlencode(params)
+            url = f"{url}?{query}"
+
+        req = urllib.request.Request(
+            url,
+            headers=self._merged_headers(headers),
+            method="GET",
+        )
+        return self._send(req)
+
+    def post(
+        self,
+        url: str,
+        data: dict[str, str] | None = None,
+        headers: dict[str, str] | None = None,
+    ) -> HttpResponse:
+        body = (
+            urllib.parse.urlencode(data).encode()
+            if data else None
+        )
+
+        merged = self._merged_headers(headers)
+        if data and "Content-Type" not in merged:
+            merged["Content-Type"] = (
+                "application/x-www-form-urlencoded"
+            )
+
+        req = urllib.request.Request(
+            url,
+            data=body,
+            headers=merged,
+            method="POST",
+        )
+        return self._send(req)
+
+    def _send(self, req: urllib.request.Request) -> HttpResponse:
+        try:
+            with self._opener.open(
+                req, timeout=self._timeout
+            ) as resp:
+                return HttpResponse(
+                    status_code=resp.getcode(),
+                    headers=dict(resp.getheaders()),
+                    data=resp.read(),
+                )
+        except urllib.error.HTTPError as e:
+            return HttpResponse(
+                status_code=e.code,
+                headers=dict(e.headers.items()),
+                data=e.read(),
+            )
+
+    def _merged_headers(
+        self, extra: dict[str, str] | None
+    ) -> dict[str, str]:
+        merged = dict(self._default_headers)
+        if extra:
+            merged.update(extra)
+        return merged
+
+
 def _request(
     url: str,
     method: str = "GET",