feat: extract shared infrastructure from shared_lib

Phase 1-3 of decoupling plan:
- Shared DB, models, infrastructure, browser, config, utils
- Event infrastructure (domain_events outbox, bus, processor)
- Structured logging
- Generic container concept (container_type/container_id)
- Alembic migrations for all schema changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infrastructure/context.py

@@ -0,0 +1,58 @@
+"""
+Base template context shared by all apps.
+
+This module no longer imports cart or menu_items services directly.
+Each app provides its own context_fn that calls this base and adds
+app-specific variables (cart data, menu_items, etc.).
+"""
+from __future__ import annotations
+
+from datetime import datetime
+
+from quart import request, g, current_app
+
+from shared.config import config
+from shared.utils import host_url
+from shared.browser.app.utils import current_route_relative_path
+
+
+async def base_context() -> dict:
+    """
+    Common template variables available in every app.
+
+    Does NOT include cart, calendar_cart_entries, total, calendar_total,
+    or menu_items — those are added by each app's context_fn.
+    """
+    is_htmx = request.headers.get("HX-Request") == "true"
+    search = request.headers.get("X-Search", "")
+    zap_filter = is_htmx and search == ""
+
+    def base_url():
+        return host_url()
+
+    hx_select = "#main-panel"
+    hx_select_search = (
+        hx_select
+        + ", #search-mobile, #search-count-mobile, #search-desktop, #search-count-desktop, #menu-items-nav-wrapper"
+    )
+
+    return {
+        "is_htmx": is_htmx,
+        "request": request,
+        "now": datetime.now(),
+        "current_local_href": current_route_relative_path(),
+        "config": config(),
+        "asset_url": current_app.jinja_env.globals.get("asset_url", lambda p: ""),
+        "sort_options": [
+            ("az", "A\u2013Z", "order/a-z.svg"),
+            ("za", "Z\u2013A", "order/z-a.svg"),
+            ("price-asc", "\u00a3 low\u2192high", "order/l-h.svg"),
+            ("price-desc", "\u00a3 high\u2192low", "order/h-l.svg"),
+        ],
+        "zap_filter": zap_filter,
+        "print": print,
+        "base_url": base_url,
+        "base_title": config()["title"],
+        "hx_select": hx_select,
+        "hx_select_search": hx_select_search,
+    }