chore: rename module + references to tiennm99/ghstats-cards

Matches the Marketplace name; repo is being renamed in lockstep.

- go.mod module path: github.com/tiennm99/ghstats →
  github.com/tiennm99/ghstats-cards
- Import paths across every .go file updated.
- README badges, install snippets, and the 'go install' line point
  to the new URL/path.
- docs/deployment-guide.md workflow template, Docker image path, and
  release edit URL updated.

Breaking for consumers pinned to the old URL; they need to swap
tiennm99/ghstats → tiennm99/ghstats-cards in workflows and switch
Docker pulls to ghcr.io/tiennm99/ghstats-cards. GitHub's HTTP
redirect covers git clones but GHCR does NOT redirect — users must
update image URIs manually.

docs/deployment-guide.md

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: tiennm99/ghstats@v1
+      - uses: tiennm99/ghstats-cards@v1
         with:
           user: ${{ github.repository_owner }}
           token: ${{ secrets.GHSTATS_TOKEN }}
@@ -77,7 +77,7 @@ Install:
 
 ```sh
 # Linux x86_64 example
-curl -L https://github.com/tiennm99/ghstats/releases/latest/download/ghstats_linux_amd64.tar.gz \
+curl -L https://github.com/tiennm99/ghstats-cards/releases/latest/download/ghstats_linux_amd64.tar.gz \
   | tar xz
 ./ghstats -user YOUR_USERNAME
 ```
@@ -85,21 +85,21 @@ curl -L https://github.com/tiennm99/ghstats/releases/latest/download/ghstats_lin
 ## 3. go install
 
 ```sh
-go install github.com/tiennm99/ghstats@latest
+go install github.com/tiennm99/ghstats-cards@latest
 ```
 
 Requires Go 1.26+. Puts the binary in `$(go env GOPATH)/bin`.
 
 ## Docker image
 
-Published to `ghcr.io/tiennm99/ghstats:<tag>` on each `v*` release via `.github/workflows/release.yml` (buildx, multi-tag: exact version, major.minor, major, latest).
+Published to `ghcr.io/tiennm99/ghstats-cards:<tag>` on each `v*` release via `.github/workflows/release.yml` (buildx, multi-tag: exact version, major.minor, major, latest).
 
 The Action itself uses a runner-built image by default (`image: Dockerfile` in `action.yml`). To switch to the pre-built image for faster cold starts, edit `action.yml`:
 
 ```yaml
 runs:
   using: docker
-  image: docker://ghcr.io/tiennm99/ghstats:v1
+  image: docker://ghcr.io/tiennm99/ghstats-cards:v1
 ```
 
 ## Release process
@@ -113,7 +113,7 @@ runs:
 5. **Marketplace publishing (one-time per repo):** GitHub only exposes the
    "Publish this Action to the GitHub Marketplace" toggle on the Release
    web UI — there is no CLI flag. Open the newly created release at
-   `https://github.com/tiennm99/ghstats/releases/tag/vX.Y.Z/edit`, tick the
+   `https://github.com/tiennm99/ghstats-cards/releases/tag/vX.Y.Z/edit`, tick the
    marketplace checkbox, accept the terms, and re-publish. Subsequent
    releases inherit marketplace visibility automatically.