Added documentation and installer support for the github secondary mirror

docs/installation.md

@@ -10,22 +10,36 @@ matches how you manage software on the host.
 
 ## Pre-built binary (recommended)
 
-Releases are published to the [Gitea releases
-page](https://git.cer.sh/axodouble/quptime/releases) with a
-`SHA256SUMS` file. Two architectures are built: `linux-amd64` and
-`linux-arm64`.
+Every tag triggers identical builds on both sources, so either one
+serves the same artefact set. Gitea is the canonical home; GitHub is a
+push-mirror.
+
+Primary — Gitea releases:
+<https://git.cer.sh/axodouble/quptime/releases>
+
+Fallback — GitHub releases (mirrored from the same tag):
+<https://github.com/Axodouble/QUptime/releases>
+
+Each release ships `qu-${TAG}-linux-amd64`, `qu-${TAG}-linux-arm64`,
+and a `SHA256SUMS` file.
 
 ```sh
 # Always pin to a tag — `latest` resolves on the server side.
-TAG=v0.1.0
+TAG=v0.0.1
 ARCH=amd64   # or arm64
 
+# Primary: Gitea
 curl -fSL -o qu \
   "https://git.cer.sh/axodouble/quptime/releases/download/${TAG}/qu-${TAG}-linux-${ARCH}"
 curl -fSL -o SHA256SUMS \
   "https://git.cer.sh/axodouble/quptime/releases/download/${TAG}/SHA256SUMS"
 
-# Verify before installing.
+# (or the GitHub mirror — substitute the host below if Gitea is unreachable)
+#   https://github.com/Axodouble/QUptime/releases/download/${TAG}/qu-${TAG}-linux-${ARCH}
+#   https://github.com/Axodouble/QUptime/releases/download/${TAG}/SHA256SUMS
+
+# Verify before installing. Use the SHA256SUMS from the SAME source
+# as the binary — never mix.
 sha256sum --check --ignore-missing SHA256SUMS
 
 install -m 0755 qu /usr/local/bin/qu
@@ -34,31 +48,37 @@ install -m 0755 qu /usr/local/bin/qu
 ## One-line install script
 
 The repo ships an `install.sh` that handles the download, checksum,
-shell-completion installation, and a default systemd unit file. Run it
+shell-completion installation, and a hardened systemd unit. Run it
 under `sudo` so it can write to `/usr/local/bin` and
 `/etc/systemd/system`.
 
 ```sh
 curl -fsSL https://git.cer.sh/Axodouble/QUptime/raw/branch/master/install.sh | sudo bash
+# or, via the GitHub mirror:
+# curl -fsSL https://raw.githubusercontent.com/Axodouble/QUptime/master/install.sh | sudo bash
 ```
 
 What it does:
 
-1. Looks up the latest release via the Gitea API.
-2. Downloads the binary to `/usr/local/bin/qu`.
+1. Looks up the latest release via the Gitea API; falls back to the
+   GitHub API if Gitea is unreachable.
+2. Downloads the per-arch binary and the matching `SHA256SUMS` from
+   the same source, then verifies the checksum. Refuses to install on
+   a mismatch.
 3. Installs bash / zsh / fish completion if a target directory exists.
-4. Writes `/etc/systemd/system/qu-serve.service` and enables it (but
-   does **not** start it — you need to run `qu init` first).
-
-The unit it writes is minimal. For a production unit with hardening,
-see the [systemd deployment guide](deployment/systemd.md).
+4. Creates a dedicated `quptime` system user and writes
+   `/etc/systemd/system/quptime.service` (hardened — matches the unit
+   in [systemd.md](deployment/systemd.md)). Enables but does not start
+   the service, so you can configure identity before first boot.
 
 ## Build from source
 
 Requires Go 1.24.2 or newer.
 
 ```sh
+# Either remote — Gitea is canonical, GitHub is a push-mirror.
 git clone https://git.cer.sh/axodouble/quptime.git
+# git clone https://github.com/Axodouble/QUptime.git
 cd quptime
 go build -ldflags "-X main.version=$(git describe --tags --always)" -o qu ./cmd/qu
 
@@ -74,15 +94,26 @@ CGO_ENABLED=0 go build -trimpath -ldflags "-s -w" -o qu ./cmd/qu
 
 ## Docker image
 
-A multi-arch (`amd64` + `arm64`) image is published to the Gitea
-registry on every tag and every push to `master`:
+The same multi-arch (`amd64` + `arm64`) image is published to two
+registries on every tag. The Gitea registry is the canonical source
+and also gets canary `:master` builds; GHCR is a tag-only mirror.
+
+Primary — Gitea registry:
 
 ```
-git.cer.sh/axodouble/quptime:master   # tip of main
+git.cer.sh/axodouble/quptime:master   # tip of main (canary)
 git.cer.sh/axodouble/quptime:latest   # latest tagged release
 git.cer.sh/axodouble/quptime:v0.0.1   # pinned release
 ```
 
+Fallback — GitHub Container Registry:
+
+```
+ghcr.io/axodouble/quptime:latest      # latest tagged release
+ghcr.io/axodouble/quptime:v0.0.1      # pinned release
+ghcr.io/axodouble/quptime:0.0         # latest 0.0.x
+```
+
 See the [Docker deployment guide](deployment/docker.md) for compose
 files and volume layout.