contact messages: contact settings in /_api/settings, ?lang overrides

GET reports contact_enabled/label/email/subject; with a translation
?lang= it also reports the per-language label/subject overrides (*_tr).
PUT accepts the contact fields; with a translation ?lang= only the
label/subject apply, written as overrides into the chunk-keyed trans
store (i18n.set_string_translation) — empty or the original's text
drops the override.

pagerite/api.py

@@ -24,7 +24,7 @@ from html5tagger import E
 from pydantic import BaseModel
 
 from pagerite import i18n, messages, views
-from pagerite.chunks import store_chunks
+from pagerite.chunks import chunk_key, store_chunks
 from pagerite.data import (
     Node,
     append_order,
@@ -276,12 +276,18 @@ async def update_structure(op: StructureOp, request: Request) -> None:
 
 
 @router.get("/_api/settings")
-async def get_settings() -> dict:
+async def get_settings(lang: str | None = None) -> dict:
     """Site-wide settings (brand, theme, custom CSS and favicon URL), plus
     the themes, banner designs and user fonts available on disk for the
     selectors, the translator service keys and the wanted translation
-    languages (for the /_translate socket)."""
-    return {
+    languages (for the /_translate socket), and the contact-messaging
+    configuration.
+
+    With a ``?lang=`` translation language the contact label/subject also
+    come out as ``*_tr`` (their per-language override, "" = none — the
+    site settings' messaging section edits those, falling back to the
+    original it edits without the query)."""
+    out = {
         "brand": data.brand,
         "brand_html": data.brand_html,
         "theme": data.theme,
@@ -296,11 +302,23 @@ async def get_settings() -> dict:
         # Unanswered contact threads: the corner ✉️ icon's badge for
         # admins (this probe runs on every page load; no polling).
         "contact_unread": messages.unread_count(),
+        "contact_enabled": data.contact_enabled,
+        "contact_label": data.contact_label,
+        "contact_email": data.contact_email,
+        "contact_subject": data.contact_subject,
         # The site default primary language: the front page's resolved
         # setting (every page may override it, inherited down the tree).
         "primary_lang": i18n.primary_lang(data.menu, ""),
         "translate_langs": sorted(data.translate_langs),
     }
+    tag = i18n.base_tag(lang or "")
+    if tag and tag != out["primary_lang"]:
+        for field in ("contact_label", "contact_subject"):
+            original = getattr(data, field) or ("Contact us" if field == "contact_label" else "")
+            out[f"{field}_tr"] = (
+                data.trans.get(chunk_key(original), {}).get(tag, "") if original else ""
+            )
+    return out
 
 
 class SettingsIn(BaseModel):
@@ -313,17 +331,56 @@ class SettingsIn(BaseModel):
     transition: str = "cube"
     translate_langs: list[str] | None = None  # None keeps the current set
     translate_keys: dict[str, str] | None = None  # None keeps the current keys
+    contact_enabled: bool | None = None  # None keeps the current setting
+    contact_label: str | None = None
+    contact_email: str | None = None
+    contact_subject: str | None = None
 
 
 @router.put("/_api/settings", status_code=204)
-async def put_settings(settings: SettingsIn, request: Request) -> None:
-    """Update site-wide settings; invalidates cached pages and ETags."""
+async def put_settings(
+    settings: SettingsIn, request: Request, lang: str | None = None
+) -> None:
+    """Update site-wide settings; invalidates cached pages and ETags.
+
+    With a ``?lang=`` translation language only the contact label/subject
+    apply — as per-language overrides in the chunk-keyed trans store, the
+    same storage machine translations use (i18n.set_string_translation);
+    empty or the original's text drops the override."""
+    tag = i18n.base_tag(lang or "")
+    if tag and tag != i18n.primary_lang(data.menu, ""):
+        with kanta.transaction(
+            f"settings:{tag}", user=request.headers.get("remote-user")
+        ):
+            changed = False
+            for field in ("contact_label", "contact_subject"):
+                value = getattr(settings, field)
+                if value is None:
+                    continue
+                original = getattr(data, field) or (
+                    "Contact us" if field == "contact_label" else ""
+                )
+                if original:
+                    changed |= i18n.set_string_translation(
+                        data, tag, original, value.strip()
+                    )
+            if changed:
+                _invalidate_pages()
+        return
     with kanta.transaction("settings", user=request.headers.get("remote-user")):
         data.brand = settings.brand
         data.brand_html = settings.brand_html
         data.theme = settings.theme
         data.custom_css = settings.custom_css
         data.transition = settings.transition
+        if settings.contact_enabled is not None:
+            data.contact_enabled = settings.contact_enabled
+        if settings.contact_label is not None:
+            data.contact_label = settings.contact_label.strip()
+        if settings.contact_email is not None:
+            data.contact_email = settings.contact_email.strip()
+        if settings.contact_subject is not None:
+            data.contact_subject = settings.contact_subject.strip()
         if settings.translate_langs is not None:
             # Any language may be a target — including the site default
             # (an article in another language can be translated INTO it);