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)

federation/bp/identity/routes.py

@@ -0,0 +1,108 @@
+"""Username selection flow.
+
+Users must choose a preferred_username before they can publish.
+This creates their ActorProfile with RSA keys.
+"""
+from __future__ import annotations
+
+import re
+
+from quart import (
+    Blueprint, request, render_template, redirect, url_for, g, abort,
+)
+
+from shared.services.registry import services
+
+
+# Username rules: 3-32 chars, lowercase alphanumeric + underscores
+USERNAME_RE = re.compile(r"^[a-z][a-z0-9_]{2,31}$")
+
+# Reserved usernames
+RESERVED = frozenset({
+    "admin", "administrator", "root", "system", "moderator", "mod",
+    "support", "help", "info", "postmaster", "webmaster", "abuse",
+    "federation", "activitypub", "api", "static", "media", "assets",
+    "well-known", "nodeinfo", "inbox", "outbox", "followers", "following",
+})
+
+
+def register(url_prefix="/identity"):
+    bp = Blueprint("identity", __name__, url_prefix=url_prefix)
+
+    @bp.get("/choose-username")
+    async def choose_username_form():
+        if not g.get("user"):
+            return redirect(url_for("auth.login_form"))
+
+        # Already has a username?
+        actor = await services.federation.get_actor_by_user_id(g.s, g.user.id)
+        if actor:
+            return redirect(url_for("activitypub.actor_profile", username=actor.preferred_username))
+
+        return await render_template("federation/choose_username.html")
+
+    @bp.post("/choose-username")
+    async def choose_username():
+        if not g.get("user"):
+            abort(401)
+
+        # Already has a username?
+        existing = await services.federation.get_actor_by_user_id(g.s, g.user.id)
+        if existing:
+            return redirect(url_for("activitypub.actor_profile", username=existing.preferred_username))
+
+        form = await request.form
+        username = (form.get("username") or "").strip().lower()
+
+        # Validate format
+        error = None
+        if not USERNAME_RE.match(username):
+            error = (
+                "Username must be 3-32 characters, start with a letter, "
+                "and contain only lowercase letters, numbers, and underscores."
+            )
+        elif username in RESERVED:
+            error = "This username is reserved."
+        elif not await services.federation.username_available(g.s, username):
+            error = "This username is already taken."
+
+        if error:
+            return await render_template(
+                "federation/choose_username.html",
+                error=error,
+                username=username,
+            ), 400
+
+        # Create ActorProfile with RSA keys
+        display_name = g.user.name or username
+        actor = await services.federation.create_actor(
+            g.s, g.user.id, username,
+            display_name=display_name,
+        )
+
+        # Redirect to where they were going, or their new profile
+        next_url = request.args.get("next")
+        if next_url:
+            return redirect(next_url)
+        return redirect(url_for("activitypub.actor_profile", username=actor.preferred_username))
+
+    @bp.get("/check-username")
+    async def check_username():
+        """HTMX endpoint to check username availability."""
+        username = (request.args.get("username") or "").strip().lower()
+
+        if not username:
+            return ""
+
+        if not USERNAME_RE.match(username):
+            return '<span class="text-red-600">Invalid format</span>'
+
+        if username in RESERVED:
+            return '<span class="text-red-600">Reserved</span>'
+
+        available = await services.federation.username_available(g.s, username)
+        if available:
+            return '<span class="text-green-600">Available</span>'
+        return '<span class="text-red-600">Taken</span>'
+
+    return bp