Phase 6: Replace render_template() with s-expression rendering in all GET routes

Migrate ~52 GET route handlers across all 7 services from Jinja
render_template() to s-expression component rendering. Each service
gets a sexp_components.py with page/oob/cards render functions.

- Add per-service sexp_components.py (account, blog, cart, events,
  federation, market, orders) with full page, OOB, and pagination
  card rendering
- Add shared/sexp/helpers.py with call_url, root_header_html,
  full_page, oob_page utilities
- Update all GET routes to use get_template_context() + render fns
- Fix get_template_context() to inject Jinja globals (URL helpers)
- Add qs_filter to base_context for sexp filter URL building
- Mount sexp_components.py in docker-compose.dev.yml for all services
- Import sexp_components in app.py for Hypercorn --reload watching
- Fix route_prefix import (shared.utils not shared.infrastructure.urls)
- Fix federation choose-username missing actor in context
- Fix market page_markets missing post in context

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

federation/app.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 import path_setup  # noqa: F401  # adds shared/ to sys.path
+import sexp_components  # noqa: F401  # ensure Hypercorn --reload watches this file
 from pathlib import Path
 
 from quart import g, request
@@ -93,8 +94,13 @@ def create_app() -> "Quart":
     # --- home page ---
     @app.get("/")
     async def home():
-        from quart import render_template
-        return await render_template("_types/federation/index.html")
+        from quart import make_response
+        from shared.sexp.page import get_template_context
+        from sexp_components import render_federation_home
+
+        ctx = await get_template_context()
+        html = await render_federation_home(ctx)
+        return await make_response(html)
 
     return app