Add common library for shared functionality

[niekky]

This pull request primarily updates the build configuration and submodules for the project. The main changes add support for a new common module and update the lib and mod submodules to newer versions.

Build system updates:

• Added common.c from the common module to the list of source files in the app/hotfire/rev5/Makefile, ensuring it is compiled as part of the build.
• Included the common module's directory in the include path (C_INCLUDES) in the Makefile, so its headers are available during compilation.

Submodule updates:

• Updated the lib submodule to a newer commit, which may include bug fixes or new features.
• Updated the mod submodule to a newer commit, likely bringing in changes required for the new common module integration.

[Copilot]

Pull request overview

Integrates a new shared common module into the Hotfire rev5 build by updating the Makefile so the module is compiled and its headers are discoverable.

Changes:

• Added $(MOD_DIR)/common/common.c to C_SOURCES so it is built into the firmware.
• Added -I$(MOD_DIR)/common to C_INCLUDES so common headers can be included during compilation.

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[Copilot]

This new C_SOURCES entry has a stray tab / excess whitespace before the line-continuation backslash, unlike the surrounding entries. Please remove the tab and keep spacing consistent to avoid hidden whitespace differences in Makefile edits.

Suggested change

	$(MOD_DIR)/common/common.c \
	$(MOD_DIR)/common/common.c \

[ETSells]

@niekky I don't recommend merging this. Common does not exist on the HEAD of mod, and drivers are on an entirely new submodule.

Recommend postponement to after the "potential" hotfire date (even though we both know that's unlikely to happen, it's the right move for stability).