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/static/nav-labels/new.svg

@@ -0,0 +1,14 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+     viewBox="0 0 100 100" width="100" height="100" role="img" aria-labelledby="title">
+  <title id="title">New</title>
+
+    <!-- The stripe -->
+    <rect x="0" y="30" width="100" height="40" rx="4" fill="#22c55e"/>
+    <!-- Label on the stripe (centered) -->
+    <text x="52" y="52"
+          font-family="system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif"
+          font-size="25" font-weight="800" fill="#ffffff"
+          text-anchor="middle" dominant-baseline="middle" letter-spacing=".15em">
+      NEW
+    </text>
+</svg>

shared/static/nav-labels/offer.svg

@@ -0,0 +1,16 @@
+
+
+<svg xmlns="http://www.w3.org/2000/svg"
+     viewBox="0 0 100 100" width="100" height="100" role="img" aria-labelledby="title">
+  <title id="title">Offer</title>
+
+    <!-- The stripe -->
+    <rect x="0" y="30" width="100" height="40" rx="4" fill="#22c55e"/>
+    <!-- Label on the stripe (centered) -->
+    <text x="52" y="52"
+          font-family="system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif"
+          font-size="25" font-weight="800" fill="#ffffff"
+          text-anchor="middle" dominant-baseline="middle" letter-spacing=".15em">
+      OFFER
+    </text>
+</svg>