Add accessibility attributes for screen readers

Improve accessibility by adding ARIA attributes to interactive
components:

nav.py:
- Menu button: aria_label="Open navigation menu"

sidebar.py:
- Close button: aria_label="Close menu"
- Drawer panel: role="dialog", aria_label="Navigation menu"

base.py:
- Toast container: aria_live="polite" (announces toasts)
- Event slide-over: role="dialog", aria_label="Event details"

These changes help screen readers properly announce interactive
elements and their purposes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/animaltrack/web/templates/base.py

@@ -157,6 +157,8 @@ def EventSlideOver():  # noqa: N802
             "shadow-2xl border-l border-stone-700 overflow-hidden",
             tabindex="-1",
             hx_on_keydown="if(event.key==='Escape') closeEventPanel()",
+            role="dialog",
+            aria_label="Event details",
         ),
     )
 
@@ -215,7 +217,7 @@ def page(
             cls="pb-20 md:pb-4 md:ml-60 min-h-screen bg-[#0f0f0e] text-stone-100",
         ),
         # Toast container with hx-preserve to survive body swaps for OOB toast injection
-        Div(id="fh-toast-container", hx_preserve=True),
+        Div(id="fh-toast-container", hx_preserve=True, aria_live="polite"),
         # Mobile bottom nav
         BottomNav(active_id=active_nav),
     )

src/animaltrack/web/templates/nav.py

@@ -102,6 +102,7 @@ def BottomNav(active_id: str = "eggs"):  # noqa: N802
                 onclick="openMenuDrawer()",
                 cls=wrapper_cls,
                 type="button",
+                aria_label="Open navigation menu",
             )
 
         # Regular nav items are links

src/animaltrack/web/templates/sidebar.py

@@ -264,6 +264,7 @@ def MenuDrawer(user_role: UserRole | None = None):  # noqa: N802
                     hx_on_click="closeMenuDrawer()",
                     cls="p-2 -mr-2 hover:bg-stone-800 rounded-lg transition-colors",
                     type="button",
+                    aria_label="Close menu",
                 ),
                 cls="flex items-center justify-between px-4 py-4 border-b border-stone-800",
             ),
@@ -276,6 +277,8 @@ def MenuDrawer(user_role: UserRole | None = None):  # noqa: N802
             cls="fixed top-0 right-0 bottom-0 w-72 bg-[#141413] z-50 flex flex-col shadow-2xl",
             tabindex="-1",
             hx_on_keydown="if(event.key==='Escape') closeMenuDrawer()",
+            role="dialog",
+            aria_label="Navigation menu",
         ),
         cls="md:hidden",
     )