feat(ui): add landing page with random public postcards for unauthenticated visitors

app/routers/web.py

@@ -1,5 +1,6 @@
 from datetime import datetime, timezone, timedelta
 from pathlib import Path
+from random import shuffle
 from uuid import uuid4
 
 from fastapi import APIRouter, Depends, File, Form, Query, Request, UploadFile
@@ -17,12 +18,11 @@ from app.auth import (
 )
 from app.config import SECRET_KEY, SESSION_COOKIE_NAME, UPLOAD_DIR
 from app.database import get_db
-from datetime import datetime
 from random import choice
 from string import ascii_letters, digits
 
 from app.models import InviteCode, Postcard, Profile, User
-from app.i18n import t as _t
+from app.i18n import t as _t, get_languages as _get_languages
 
 router = APIRouter(tags=["web"])
 templates = Jinja2Templates(directory=str(Path(__file__).resolve().parent.parent / "templates"))
@@ -109,6 +109,48 @@ def _redirect(url: str) -> RedirectResponse:
     return RedirectResponse(url, status_code=303)
 
 
+# ---------- Root / Index ----------
+
+@router.get("/", response_class=HTMLResponse)
+def index_page(request: Request, db: Session = Depends(get_db)):
+    user = redirect_if_not_logged_in(request, db)
+    if user:
+        return _redirect("/dashboard")
+
+    # Collect all public postcards from all users with showcase enabled
+    all_postcards: list[Postcard] = []
+    users = db.query(User).filter(User.showcase_mode.isnot(None)).all()
+    for u in users:
+        profiles = db.query(Profile).filter(
+            Profile.user_id == u.id, Profile.showcase_enabled == True
+        ).all()
+        for p in profiles:
+            cards = db.query(Postcard).filter(
+                Postcard.profile_id == p.id, Postcard.showcase_hidden == False
+            ).all()
+            for c in cards:
+                visible = True
+                if c.status in ("sent", "delivered") and p.showcase_visible not in ("sent", "both"):
+                    visible = False
+                if c.status == "received" and p.showcase_visible not in ("received", "both"):
+                    visible = False
+                if visible:
+                    all_postcards.append(c)
+
+    shuffle(all_postcards)
+
+    lang = request.query_params.get("lang")
+    avail = _get_languages()
+    if not lang or lang not in avail:
+        lang = request.cookies.get("showcase_lang")
+    if not lang or lang not in avail:
+        lang = "zh"
+
+    return templates.TemplateResponse("index.html", {
+        "request": request, "postcards": all_postcards, "lang": lang,
+    })
+
+
 # ---------- Auth ----------
 
 @router.get("/login", response_class=HTMLResponse)