chore(llama-cpp): re-pin to upstream #24316, drop vendored stdin patch

Upstream replaced the ad-hoc video stdin handling with a proper RAII
refactor (ggml-org/llama.cpp#24316, "mtmd: refactor video subproc
handling"), which includes the same `sp->stdin_file = nullptr` guard our
patch added (plus join-before-destroy ordering). Re-pin LLAMA_VERSION to
that branch head and drop patches/0001 - it's now redundant.

Verified e2e with gemma-4-e2b-it-qat-q4_0: no crash, video frames decode
and the model answers correctly (red clip -> "Red", blue -> "Blue").

NOTE: #24316 is not yet merged, so this pins to its branch-head commit
(28ca1e60). Re-pin to the squash-merge commit on master once it lands,
otherwise `git fetch` may lose the commit after the branch is deleted.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

backend/cpp/llama-cpp/Makefile

@@ -1,5 +1,5 @@
 
-LLAMA_VERSION?=8f83d6c271d194bde2d410145a0ce73bc42e85cd
+LLAMA_VERSION?=28ca1e600c5dac1854fb7e09611914013430b037
 LLAMA_REPO?=https://github.com/ggerganov/llama.cpp
 
 CMAKE_ARGS?=

backend/cpp/llama-cpp/patches/0001-mtmd-fix-video-stdin-double-close.patch

@@ -1,30 +0,0 @@
-From: Ettore Di Giacinto <mudler@localai.io>
-Subject: [PATCH] mtmd: fix double-close of ffmpeg/ffprobe stdin in video helper
-
-mtmd_helper_video::feed_stdin() obtains the subprocess stdin via
-subprocess_stdin(sp), which returns sp->stdin_file directly, then
-fclose()s that FILE. Closing the local copy leaves sp->stdin_file
-dangling (still non-NULL), so the subsequent subprocess_destroy()
-fclose()s the same FILE a second time. The resulting heap corruption
-aborts the process ("corrupted double-linked list" / "corrupted size
-vs. prev_size") - notably on the server's base64 input_video path,
-where every probe()/start_ffmpeg() feeds the buffer via stdin. The CLI
---video file path is unaffected (it never spawns the stdin feeder).
-
-Clear sp->stdin_file after fclose so subprocess_destroy() skips it.
-
---- a/tools/mtmd/mtmd-helper.cpp
-+++ b/tools/mtmd/mtmd-helper.cpp
-@@ -642,7 +642,12 @@
-         LOG_DBG("%s: feeding %zu bytes to stdin\n", __func__, input_buf.size());
-         size_t written = fwrite(input_buf.data(), 1, input_buf.size(), f);
-         LOG_DBG("%s: wrote %zu bytes, closing stdin\n", __func__, written);
-         fclose(f);
-+        // subprocess_stdin() returns sp->stdin_file directly; fclosing our local
-+        // copy leaves the struct pointer dangling, so subprocess_destroy() would
-+        // fclose() the same FILE again -> heap corruption. Null it so the later
-+        // destroy skips stdin.
-+        sp->stdin_file = nullptr;
-     }
-
-     bool probe(float fps_target_arg) {