feat(storage): add S3 image storage support with file-based config and migration script

app/routers/web.py

@@ -16,7 +16,7 @@ from app.auth import (
     redirect_if_not_logged_in,
     verify_password,
 )
-from app.config import SECRET_KEY, SESSION_COOKIE_NAME, UPLOAD_DIR
+from app.config import SECRET_KEY, SESSION_COOKIE_NAME
 from app.database import get_db
 from random import choice
 from string import ascii_letters, digits
@@ -86,6 +86,10 @@ def _translate_filter(key: str, lang: str = "zh") -> str:
 
 templates.env.filters["t"] = _translate_filter
 
+# image URL resolver: bare key → full URL (local /uploads/... or S3 public URL)
+from app.storage import resolve_url as _resolve_image_url
+templates.env.filters["image_url"] = lambda v: _resolve_image_url(v) if v else ""
+
 from app.i18n import get_languages as _get_languages
 templates.env.globals["available_languages"] = _get_languages()
 
@@ -188,7 +192,7 @@ def api_public_cards(
         "page": page,
         "has_more": start + limit < total,
         "cards": [{
-            "image_front": c.image_front,
+            "image_front": _resolve_image_url(c.image_front),
             "country_from": c.country_from,
             "country_to": c.country_to,
             "status": c.status,
@@ -230,7 +234,7 @@ def api_public_cards_user(
         "page": page,
         "has_more": start + limit < total,
         "cards": [{
-            "image_front": c.image_front,
+            "image_front": _resolve_image_url(c.image_front),
             "country_from": c.country_from,
             "country_to": c.country_to,
         } for c in batch],
@@ -959,12 +963,13 @@ async def upload_image(
     )
     if not pc:
         return _redirect("/profiles")
+    from app.storage import get_storage
+    storage = get_storage()
     ext = Path(file.filename or "upload.jpg").suffix or ".jpg"
-    filename = f"{uuid4().hex}{ext}"
-    dest = UPLOAD_DIR / filename
+    key = f"{uuid4().hex}{ext}"
     content = await file.read()
-    dest.write_bytes(content)
-    setattr(pc, f"image_{side}", f"/uploads/{filename}")
+    storage.put(key, content)
+    setattr(pc, f"image_{side}", key)
     db.commit()
     return _redirect(f"/postcards/{postcard_id}")