feat(inline): answer from the link cache, and put the answer on the trait

Inline results were URL-only: Telegram fetches an inline result's URL itself
and cannot send site headers, so every pixiv item (and every locally encoded
ugoira/bsky MP4) was skipped and such a query answered empty. A post that is
already in the link cache now answers with InlineQueryResultCached* built
from its Telegram file ids — no fetch, no upload, and the hotlink-protected
case simply works. A degraded entry (file ids gone) falls back to URLs, and
there a video with no poster is skipped (Telegram would try to render the
mp4 as its own thumbnail).

The answer call moves onto MediaSender (answer_inline_query, mirroring the
other user-flow methods), which is what makes the path testable at all: the
two new tests drive the cache answer and the degraded/empty answer through
TestStores + MockSender, which recorded nothing about inline before.

The result builders are shared by both paths now (url_result/cached_result +
inline_kind), so the fetch path's behaviour is unchanged.

crates/xmedia-bot/src/media_sender/mod.rs

@@ -8,8 +8,8 @@ use teloxide::RequestError;
 use teloxide::prelude::Requester;
 use teloxide::prelude::*;
 use teloxide::types::{
-    CallbackQueryId, ChatAction, ChatId, InlineKeyboardMarkup, InputFile, InputMedia, Message,
-    MessageId, ParseMode, ReplyParameters,
+    CallbackQueryId, ChatAction, ChatId, InlineKeyboardMarkup, InlineQueryId, InlineQueryResult,
+    InputFile, InputMedia, Message, MessageId, ParseMode, ReplyParameters,
 };
 
 /// Boxed, `Send` future returned by a [`MediaSender`] method (`async fn` in
@@ -60,6 +60,17 @@ pub trait MediaSender: Send + Sync {
         reply_markup: Option<InlineKeyboardMarkup>,
     ) -> BoxFuture<'_, Result<i64, RequestError>>;
 
+    /// Answers an inline query with `results`, cached by Telegram for
+    /// `cache_time` seconds. An empty `results` answers *empty*, which is a
+    /// real answer: it stops the client spinning and lets Telegram serve a
+    /// repeat itself instead of the bot re-running the query.
+    fn answer_inline_query(
+        &self,
+        id: InlineQueryId,
+        results: Vec<InlineQueryResult>,
+        cache_time: u32,
+    ) -> BoxFuture<'_, Result<(), RequestError>>;
+
     /// Answers a callback query, optionally with a toast `text` shown to the
     /// user who pressed the button.
     fn answer_callback_query(
@@ -186,6 +197,20 @@ impl MediaSender for Bot {
         })
     }
 
+    fn answer_inline_query(
+        &self,
+        id: InlineQueryId,
+        results: Vec<InlineQueryResult>,
+        cache_time: u32,
+    ) -> BoxFuture<'_, Result<(), RequestError>> {
+        Box::pin(async move {
+            <Bot as Requester>::answer_inline_query(self, id, results)
+                .cache_time(cache_time)
+                .await
+                .map(|_| ())
+        })
+    }
+
     fn answer_callback_query(
         &self,
         id: CallbackQueryId,