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>

socktop_agent/Cargo.toml

@@ -6,6 +6,8 @@ description = "Socktop agent daemon. Serves host metrics over WebSocket."
 edition = "2024"
 license = "MIT"
 readme = "README.md"
+homepage = "https://github.com/jasonwitty/socktop"
+repository = "https://github.com/jasonwitty/socktop"
 
 [dependencies]
 # Tokio: Use minimal features instead of "full" to reduce binary size
@@ -21,7 +23,7 @@ flate2 = { version = "1", default-features = false, features = ["rust_backend"]
 futures-util = "0.3.31"
 tracing = { version = "0.1", optional = true }
 tracing-subscriber = { version = "0.3", features = ["env-filter"], optional = true }
-gfxinfo = "0.1.2"
+gfxinfo = { version = "0.1.2", optional = true }
 once_cell = "1.19"
 axum-server = { version = "0.7", features = ["tls-rustls"] }
 rustls = { version = "0.23", features = ["aws-lc-rs"] }
@@ -33,7 +35,8 @@ prost = { workspace = true }
 time = { version = "0.3", default-features = false, features = ["formatting", "macros", "parsing" ] }
 
 [features]
-default = []
+default = ["gpu"]
+gpu = ["gfxinfo"]
 logging = ["tracing", "tracing-subscriber"]
 
 [build-dependencies]
@@ -45,3 +48,21 @@ protoc-bin-vendored = "3"
 assert_cmd = "2.0"
 tempfile = "3.10"
 tokio-tungstenite = "0.21"
+
+[package.metadata.deb]
+maintainer = "Jason Witty <jasonpwitty+socktop@proton.me>"
+copyright = "2024, Jason Witty <jasonpwitty+socktop@proton.me>"
+license-file = ["../LICENSE", "4"]
+extended-description = """\
+socktop_agent is the daemon component that runs on remote hosts to collect \
+and serve system metrics over WebSocket. It gathers CPU, memory, disk, network, \
+GPU, and process information that can be monitored remotely by the socktop TUI client."""
+depends = "$auto"
+section = "admin"
+priority = "optional"
+assets = [
+    ["target/release/socktop_agent", "usr/bin/", "755"],
+    ["../README.md", "usr/share/doc/socktop_agent/", "644"],
+]
+maintainer-scripts = "debian/"
+systemd-units = { unit-name = "socktop-agent", unit-scripts = ".", enable = false }