Monorepo: consolidate 7 repos into one

Combines shared, blog, market, cart, events, federation, and account
into a single repository. Eliminates submodule sync, sibling model
copying at build time, and per-app CI orchestration.

Changes:
- Remove per-app .git, .gitmodules, .gitea, submodule shared/ dirs
- Remove stale sibling model copies from each app
- Update all 6 Dockerfiles for monorepo build context (root = .)
- Add build directives to docker-compose.yml
- Add single .gitea/workflows/ci.yml with change detection
- Add .dockerignore for monorepo build context
- Create __init__.py for federation and account (cross-app imports)

shared/browser/templates/macros/stickers.html

@@ -0,0 +1,24 @@
+{% macro sticker(src, title, enabled, size=40, found=false) -%}
+
+  <span class="relative inline-flex items-center justify-center group"
+      tabindex="0" aria-label="{{ title|capitalize }}">
+    <!-- sticker icon -->
+    <img
+      src="{{ src }}"
+      width="{{size}}" height="{{size}}"
+      alt="{{ title|capitalize }}"
+      title="{{ title|capitalize }}"
+      class="{% if found %}border-2 border-yellow-200 bg-yellow-300{% endif %} {%if enabled %} opacity-100 {% else %} opacity-40 saturate-0 {% endif %}"
+    />
+
+    <!-- tooltip -->
+    <span role="tooltip"
+          class="pointer-events-none absolute z-50 bottom-full left-1/2 -translate-x-1/2 mb-2 hidden group-hover/tt:block group-focus-visible/tt:block whitespace-nowrap rounded-md bg-stone-900 text-white text-xs px-2 py-1 shadow-lg">
+      {{ title|capitalize if title|lower != 'sugarfree' else 'Sugar' }}
+      <!-- little arrow -->
+      <span class="absolute top-full left-1/2 -translate-x-1/2 border-4 border-transparent border-t-stone-900"></span>
+    </span>
+  </span>
+
+{%- endmacro -%}
+