feat: Add floating sidebar navigation and dark theme support

- Add floating pill-shaped sidebar with navigation icons
- Implement dark/light theme toggle with localStorage persistence
- Update all figure factories for transparent backgrounds
- Use carto-darkmatter map style for choropleths
- Add methodology link button to Toronto dashboard header
- Add back to dashboard button on methodology page
- Remove social links from home page (now in sidebar)
- Update CLAUDE.md to Sprint 7

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

portfolio_app/components/__init__.py

@@ -2,11 +2,13 @@
 
 from .map_controls import create_map_controls, create_metric_selector
 from .metric_card import MetricCard, create_metric_cards_row
+from .sidebar import create_sidebar
 from .time_slider import create_time_slider, create_year_selector
 
 __all__ = [
     "create_map_controls",
     "create_metric_selector",
+    "create_sidebar",
     "create_time_slider",
     "create_year_selector",
     "MetricCard",

portfolio_app/components/sidebar.py

@@ -0,0 +1,179 @@
+"""Floating sidebar navigation component."""
+
+import dash_mantine_components as dmc
+from dash import dcc, html
+from dash_iconify import DashIconify
+
+# Navigation items configuration
+NAV_ITEMS = [
+    {"path": "/", "icon": "tabler:home", "label": "Home"},
+    {"path": "/toronto", "icon": "tabler:map-2", "label": "Toronto Housing"},
+]
+
+# External links configuration
+EXTERNAL_LINKS = [
+    {
+        "url": "https://github.com/leomiranda",
+        "icon": "tabler:brand-github",
+        "label": "GitHub",
+    },
+    {
+        "url": "https://linkedin.com/in/leobmiranda",
+        "icon": "tabler:brand-linkedin",
+        "label": "LinkedIn",
+    },
+]
+
+
+def create_brand_logo() -> html.Div:
+    """Create the brand initials logo."""
+    return html.Div(
+        dcc.Link(
+            "LM",
+            href="/",
+            className="sidebar-brand-link",
+        ),
+        className="sidebar-brand",
+    )
+
+
+def create_nav_icon(
+    icon: str,
+    label: str,
+    path: str,
+    current_path: str,
+) -> dmc.Tooltip:
+    """Create a navigation icon with tooltip.
+
+    Args:
+        icon: Iconify icon string.
+        label: Tooltip label.
+        path: Navigation path.
+        current_path: Current page path for active state.
+
+    Returns:
+        Tooltip-wrapped navigation icon.
+    """
+    is_active = current_path == path or (path != "/" and current_path.startswith(path))
+
+    return dmc.Tooltip(
+        dcc.Link(
+            dmc.ActionIcon(
+                DashIconify(icon=icon, width=20),
+                variant="subtle" if not is_active else "filled",
+                size="lg",
+                radius="xl",
+                color="blue" if is_active else "gray",
+                className="nav-icon-active" if is_active else "",
+            ),
+            href=path,
+        ),
+        label=label,
+        position="right",
+        withArrow=True,
+    )
+
+
+def create_theme_toggle(current_theme: str = "dark") -> dmc.Tooltip:
+    """Create the theme toggle button.
+
+    Args:
+        current_theme: Current theme ('dark' or 'light').
+
+    Returns:
+        Tooltip-wrapped theme toggle icon.
+    """
+    icon = "tabler:sun" if current_theme == "dark" else "tabler:moon"
+    label = "Switch to light mode" if current_theme == "dark" else "Switch to dark mode"
+
+    return dmc.Tooltip(
+        dmc.ActionIcon(
+            DashIconify(icon=icon, width=20, id="theme-toggle-icon"),
+            id="theme-toggle",
+            variant="subtle",
+            size="lg",
+            radius="xl",
+            color="gray",
+        ),
+        label=label,
+        position="right",
+        withArrow=True,
+    )
+
+
+def create_external_link(url: str, icon: str, label: str) -> dmc.Tooltip:
+    """Create an external link icon with tooltip.
+
+    Args:
+        url: External URL.
+        icon: Iconify icon string.
+        label: Tooltip label.
+
+    Returns:
+        Tooltip-wrapped external link icon.
+    """
+    return dmc.Tooltip(
+        dmc.Anchor(
+            dmc.ActionIcon(
+                DashIconify(icon=icon, width=20),
+                variant="subtle",
+                size="lg",
+                radius="xl",
+                color="gray",
+            ),
+            href=url,
+            target="_blank",
+        ),
+        label=label,
+        position="right",
+        withArrow=True,
+    )
+
+
+def create_sidebar_divider() -> html.Div:
+    """Create a horizontal divider for the sidebar."""
+    return html.Div(className="sidebar-divider")
+
+
+def create_sidebar(current_path: str = "/", current_theme: str = "dark") -> html.Div:
+    """Create the floating sidebar navigation.
+
+    Args:
+        current_path: Current page path for active state highlighting.
+        current_theme: Current theme for toggle icon state.
+
+    Returns:
+        Complete sidebar component.
+    """
+    return html.Div(
+        [
+            # Brand logo
+            create_brand_logo(),
+            create_sidebar_divider(),
+            # Navigation icons
+            *[
+                create_nav_icon(
+                    icon=item["icon"],
+                    label=item["label"],
+                    path=item["path"],
+                    current_path=current_path,
+                )
+                for item in NAV_ITEMS
+            ],
+            create_sidebar_divider(),
+            # Theme toggle
+            create_theme_toggle(current_theme),
+            create_sidebar_divider(),
+            # External links
+            *[
+                create_external_link(
+                    url=link["url"],
+                    icon=link["icon"],
+                    label=link["label"],
+                )
+                for link in EXTERNAL_LINKS
+            ],
+        ],
+        className="floating-sidebar",
+        id="floating-sidebar",
+    )