Run executables directly (#645)

- Apps can be launched directly from file paths (including Files app support)
- Added executable detection to identify unsupported or invalid binaries before launch.
- App startup is now streamlined through separate registered-app and direct-execution interfaces.
- Existing app launch points were migrated to the updated startup APIs.

Modules/app-module/source/elf_check.cpp

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: Apache-2.0
+#include <app/elf_check.h>
+
+#include <cstdio>
+#include <cstring>
+
+namespace {
+
+constexpr size_t ELF_HEADER_PREFIX_SIZE = 20; // e_ident[16] + e_type(2) + e_machine(2)
+constexpr uint8_t ELF_MAGIC[4] = { 0x7f, 'E', 'L', 'F' };
+
+uint16_t read_le16(const uint8_t* bytes) {
+    return static_cast<uint16_t>(bytes[0] | (bytes[1] << 8));
+}
+
+} // namespace
+
+bool elf_check_file(const char* path, const struct ElfRequirements* requirements) {
+    FILE* file = fopen(path, "rb");
+    if (file == nullptr) {
+        return false;
+    }
+
+    uint8_t header[ELF_HEADER_PREFIX_SIZE];
+    size_t read = fread(header, 1, sizeof(header), file);
+    fclose(file);
+
+    if (read != sizeof(header)) {
+        return false;
+    }
+
+    if (memcmp(header, ELF_MAGIC, sizeof(ELF_MAGIC)) != 0) {
+        return false;
+    }
+
+    uint8_t elf_class = header[4]; // e_ident[EI_CLASS]
+    uint8_t data = header[5]; // e_ident[EI_DATA]
+    uint16_t type = read_le16(header + 16); // e_type
+    uint16_t machine = read_le16(header + 18); // e_machine
+
+    return elf_class == requirements->elf_class
+        && data == requirements->data
+        && type == requirements->type
+        && machine == requirements->machine;
+}