feat(web): add customizable input placeholder for Agent/Chatflow/Chatbot web app (#37790)

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Co-authored-by: yyh <92089059+lyzno1@users.noreply.github.com>
Co-authored-by: yyh <yuanyouhuilyz@gmail.com>
Co-authored-by: hjlarry <hjlarry@163.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/controllers/console/app/app.py

@@ -345,6 +345,7 @@ class Site(ResponseModel):
     customize_domain: str | None = None
     copyright: str | None = None
     privacy_policy: str | None = None
+    input_placeholder: str | None = None
     custom_disclaimer: str | None = None
     customize_token_strategy: str | None = None
     prompt_public: bool | None = None

api/controllers/console/app/site.py

@@ -40,6 +40,7 @@ class AppSiteUpdatePayload(BaseModel):
     customize_domain: str | None = Field(default=None)
     copyright: str | None = Field(default=None)
     privacy_policy: str | None = Field(default=None)
+    input_placeholder: str | None = Field(default=None)
     custom_disclaimer: str | None = Field(default=None)
     customize_token_strategy: Literal["must", "allow", "not_allow"] | None = Field(default=None)
     prompt_public: bool | None = Field(default=None)
@@ -66,6 +67,7 @@ class AppSiteResponse(ResponseModel):
     customize_domain: str | None = None
     copyright: str | None = None
     privacy_policy: str | None = None
+    input_placeholder: str | None = None
     custom_disclaimer: str | None = None
     customize_token_strategy: str
     prompt_public: bool
@@ -110,6 +112,7 @@ class AppSite(Resource):
             "customize_domain",
             "copyright",
             "privacy_policy",
+            "input_placeholder",
             "custom_disclaimer",
             "customize_token_strategy",
             "prompt_public",