feat: Implement Sprint 8 - Portfolio website expansion (MVP)

New pages:
- Home: Redesigned with hero, impact stats, featured project
- About: 6-section professional narrative
- Projects: Hub with 4 project cards and status badges
- Resume: Inline display with download placeholders
- Contact: Form UI (disabled) with contact info
- Blog: Markdown-based system with frontmatter support

Infrastructure:
- Blog system with markdown loader (python-frontmatter, markdown, pygments)
- Sidebar callback for active state highlighting on navigation
- Separated navigation into main pages and projects/dashboards groups

Closes #36, #37, #38, #39, #40, #41, #42, #43

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

portfolio_app/utils/markdown_loader.py

@@ -0,0 +1,109 @@
+"""Markdown article loader with frontmatter support."""
+
+from pathlib import Path
+from typing import TypedDict
+
+import frontmatter
+import markdown
+from markdown.extensions.codehilite import CodeHiliteExtension
+from markdown.extensions.fenced_code import FencedCodeExtension
+from markdown.extensions.tables import TableExtension
+from markdown.extensions.toc import TocExtension
+
+# Content directory (relative to this file's package)
+CONTENT_DIR = Path(__file__).parent.parent / "content" / "blog"
+
+
+class ArticleMeta(TypedDict):
+    """Article metadata from frontmatter."""
+
+    slug: str
+    title: str
+    date: str
+    description: str
+    tags: list[str]
+    status: str  # "published" or "draft"
+
+
+class Article(TypedDict):
+    """Full article with metadata and content."""
+
+    meta: ArticleMeta
+    content: str
+    html: str
+
+
+def render_markdown(content: str) -> str:
+    """Convert markdown to HTML with syntax highlighting.
+
+    Args:
+        content: Raw markdown string.
+
+    Returns:
+        HTML string with syntax-highlighted code blocks.
+    """
+    md = markdown.Markdown(
+        extensions=[
+            FencedCodeExtension(),
+            CodeHiliteExtension(css_class="highlight", guess_lang=False),
+            TableExtension(),
+            TocExtension(permalink=True),
+            "nl2br",
+        ]
+    )
+    return str(md.convert(content))
+
+
+def get_article(slug: str) -> Article | None:
+    """Load a single article by slug.
+
+    Args:
+        slug: Article slug (filename without .md extension).
+
+    Returns:
+        Article dict or None if not found.
+    """
+    filepath = CONTENT_DIR / f"{slug}.md"
+    if not filepath.exists():
+        return None
+
+    post = frontmatter.load(filepath)
+
+    meta: ArticleMeta = {
+        "slug": slug,
+        "title": post.get("title", slug.replace("-", " ").title()),
+        "date": str(post.get("date", "")),
+        "description": post.get("description", ""),
+        "tags": post.get("tags", []),
+        "status": post.get("status", "published"),
+    }
+
+    return {
+        "meta": meta,
+        "content": post.content,
+        "html": render_markdown(post.content),
+    }
+
+
+def get_all_articles(include_drafts: bool = False) -> list[Article]:
+    """Load all articles from the content directory.
+
+    Args:
+        include_drafts: If True, include articles with status="draft".
+
+    Returns:
+        List of articles sorted by date (newest first).
+    """
+    if not CONTENT_DIR.exists():
+        return []
+
+    articles: list[Article] = []
+    for filepath in CONTENT_DIR.glob("*.md"):
+        slug = filepath.stem
+        article = get_article(slug)
+        if article and (include_drafts or article["meta"]["status"] == "published"):
+            articles.append(article)
+
+    # Sort by date descending
+    articles.sort(key=lambda a: a["meta"]["date"], reverse=True)
+    return articles