feat: add comprehensive Playwright E2E test suite

- Create e2e/ directory with 7 test modules covering:
  - Home page: title, nav links, theme toggle, newsletter form
  - Cookie consent: accept all, reject all, granular prefs, persistence
  - Article index: loads, tag filter, click-through navigation
  - Article detail: title/read-time, share section, comments, newsletter aside, related
  - Comments: valid submit → redirect, empty body → error display, disabled check
  - Newsletter: JS confirmation message, invalid email error, aside form, duplicate
  - Feeds: RSS/sitemap/robots.txt validity, tag feed, seeded content present
- Extend seed_e2e_content management command with tagged article, about page,
  no-comments article, and legal pages for richer test coverage
- Add seed command tests (create + idempotency) to keep coverage ≥ 90%
- Add pr-e2e CI job (runs on pull_request): builds image, starts postgres + app,
  installs playwright, runs pytest e2e/
- Update nightly-e2e to run full e2e/ suite alongside legacy journey test
- Add --ignore=e2e to unit-test pytest step (coverage must not include browser tests)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

e2e/test_articles.py

@@ -0,0 +1,59 @@
+"""E2E tests for the article index page."""
+
+from __future__ import annotations
+
+import pytest
+from playwright.sync_api import Page, expect
+
+
+@pytest.mark.e2e
+def test_article_index_loads(page: Page, base_url: str) -> None:
+    page.goto(f"{base_url}/articles/", wait_until="networkidle")
+    expect(page.get_by_role("heading", level=1)).to_be_visible()
+    # At least one article card must be present after seeding
+    expect(page.locator("main article").first).to_be_visible()
+
+
+@pytest.mark.e2e
+def test_tag_filter_shows_tagged_articles(page: Page, base_url: str) -> None:
+    page.goto(f"{base_url}/articles/", wait_until="networkidle")
+    # The seeded "AI Tools" tag link must be present
+    tag_link = page.get_by_role("link", name="AI Tools")
+    expect(tag_link).to_be_visible()
+    tag_link.click()
+    page.wait_for_load_state("networkidle")
+
+    # URL should now contain ?tag=ai-tools
+    assert "tag=ai-tools" in page.url
+
+    # The tagged article must appear; no-tag articles may be absent
+    expect(page.get_by_text("Tagged Article")).to_be_visible()
+
+
+@pytest.mark.e2e
+def test_all_tag_clears_filter(page: Page, base_url: str) -> None:
+    # Start with the tag filter applied
+    page.goto(f"{base_url}/articles/?tag=ai-tools", wait_until="networkidle")
+
+    # Clicking "All" should return to unfiltered list
+    page.get_by_role("link", name="All").click()
+    page.wait_for_load_state("networkidle")
+    assert "tag=" not in page.url
+    # All seeded articles should now be visible
+    expect(page.locator("main article").first).to_be_visible()
+
+
+@pytest.mark.e2e
+def test_article_card_navigates_to_detail(page: Page, base_url: str) -> None:
+    page.goto(f"{base_url}/articles/", wait_until="networkidle")
+    first_link = page.locator("main article a").first
+    expect(first_link).to_be_visible()
+
+    href = first_link.get_attribute("href")
+    assert href, "Article card must have an href"
+
+    first_link.click()
+    page.wait_for_load_state("networkidle")
+
+    # We should be on an article detail page
+    expect(page.get_by_role("heading", level=1)).to_be_visible()