Add Debian packaging support for socktop-agent (#25)

* Add Debian packaging support with cargo-deb

- Add cargo-deb metadata to socktop and socktop_agent Cargo.toml
- Create systemd service file for socktop_agent
- Add postinst/postrm maintainer scripts for user/group management
- Create GitHub Actions workflow to build .deb packages for AMD64 and ARM64
- Add comprehensive documentation in docs/DEBIAN_PACKAGING.md
- Packages will be available as artifacts on every push
- Automatic GitHub releases for version tags

* Add summary documentation for debian packaging

* fix unit test, move to macro cargo_bin!

* hotfix for issue with socktop agent not creating ssl certificate on first launch after upgrade of axum server version.

* Add helpful post-install message to guide users on enabling socktop-agent service

* Fix CI build by installing libdrm development dependencies

* Fix package rename script - cargo-deb already includes architecture in filename

* Make GPU support optional to enable RISC-V builds without libdrm

- Add 'gpu' feature flag (enabled by default)
- Make gfxinfo dependency optional
- Provide no-op GPU metrics when gpu feature disabled
- Disable GPU support for RISC-V builds in CI (libdrm unavailable)
- All other architectures (amd64, arm64, armhf) still get GPU support

* feature gate GPU stats for arm v7

* specify correct package names.

* install aarch64-linux-gnu-gcc build dep

* specify correct package name

* add RISC-V GCC compiler

* add .cargo to gitignore to elimicate issue with riscv64-linux-gnu-gcc linker in config.toml

* add gcc-arm-linux-gnueabihf linker fore armv7

* set correct x-compile lib gcc-aarch64-linux-gnu for arm64 builds.

* add ports.ubuntu.com to sources

* Add ARM64 as a foreign architecture

* fixe for ARM64 build.

* security.ubuntu.com` aNNOYING

* apt repo github page

* copy output to apt repo

* fix secrets path

* fix secrets path

* change build dep

* Fix postinst message box alignment

* ci(deb): restrict APT publish to v* release tags

Previously the workflow built and published on every push to master
and feature/debian-packaging in addition to v* tags. That meant the
gh-pages APT repo got overwritten on every commit with same-version
.debs, causing apt clients to see a phantom "update available" each
time and burning ~5-10 min of cross-compile CI per merge.

After this change:
  - PRs into master still cross-build .debs as a sanity check.
  - v* tags build, publish to gh-pages, and create a GitHub release.
  - workflow_dispatch remains as the manual escape hatch.
  - master pushes no longer trigger this workflow (ci.yml still runs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -53,15 +53,23 @@ exec bash   # or: exec zsh / exec fish
 
 Windows (for the brave): install from https://rustup.rs with the MSVC toolchain. Yes, you’ll need Visual Studio Build Tools. You chose Windows — enjoy the ride.
 
-### Raspberry Pi / Ubuntu / PopOS (required)
+### Raspberry Pi / Ubuntu / PopOS (required for GPU support)
 
-Install GPU support with apt command below
+**Note:** GPU monitoring is only supported on x86_64 and aarch64 (64-bit ARM) platforms. ARMv7 (32-bit) and RISC-V builds do not include GPU support.
+
+For 64-bit systems with GPU support:
 
 ```bash
 sudo apt-get update
 sudo apt-get install libdrm-dev libdrm-amdgpu1
 ```
 
+For ARMv7 (32-bit Raspberry Pi), build with `--no-default-features` to disable GPU support:
+
+```bash
+cargo build --release -p socktop_agent --no-default-features
+```
+
 _Additional note for Raspberry Pi users. Please update your system to use the newest kernel available through app, kernel version 6.6+ will use considerably less overall CPU to run the agent. For example on a rpi4 the kernel < 6.6 the agent will consume .8 cpu but on the same hardware on > 6.6 the agent will consume only .2 cpu. (these numbers indicate continuous polling at web socket endpoints, when not in use the usage is 0)_
 
 ---