v0.7.1: Linux GLIBC 2.35 floor + scroll main window on short screens

Two user-reported issues.

=== GLIBC too new (reported via twitter) ===

Our linux-amd64 and linux-arm64 gnu builds were compiled on
ubuntu-latest (24.04, GLIBC 2.39), which means the resulting binaries
refuse to load on anything older:

  ./mhrv-rs: /lib/x86_64-linux-gnu/libc.so.6: version 'GLIBC_2.39'
    not found (required by ./mhrv-rs)

Users on Ubuntu 22.04 / Mint 21 (GLIBC 2.35) — the typical user in Iran
where this project's target audience lives, and where they can't
dist-upgrade because they're behind exactly the kind of network
restriction this tool exists to bypass — could not run the gnu builds
at all.

Fix: pin the linux-gnu matrix entries to ubuntu-22.04 runners. GLIBC
2.35 is now the minimum; binaries load on Ubuntu 22.04, Mint 21,
Debian 12, Fedora 36+, RHEL 9+ and everything newer.

Users on older distros (Ubuntu 20.04, CentOS 7) can still use the
static musl builds (mhrv-rs-linux-musl-amd64.tar.gz et al.) which
have no GLIBC dependency at all.

=== Short-screen laptops — main window content clipped (PR #6) ===

Co-authored fix from @v4g4b0nd-0x76 in PR #6 (manually applied to
avoid pulling in 400 lines of unrelated cargo-fmt churn):

- Wrap the CentralPanel body in ScrollArea::vertical()
  .auto_shrink([false; 2]) so everything stays reachable on short
  screens.
- Lower the min_inner_size from [420, 540] to [420, 400] so laptops
  with ~13" screens at default scaling can shrink the window without
  clipping UI elements.

Closes #6.

Co-authored-by: v4g4b0nd-0x76 <v4g4b0nd-0x76@users.noreply.github.com>

.github/workflows/release.yml

@@ -14,11 +14,17 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          # Pin to Ubuntu 22.04 (GLIBC 2.35) so the glibc builds run on any
+          # distro that's ≥ Ubuntu 22.04 / Debian 12 / Mint 21 / Fedora 36.
+          # ubuntu-latest points at 24.04 (GLIBC 2.39) which bakes in a
+          # too-new GLIBC symbol requirement and rejects loading on older
+          # distros. For users behind tight internet who literally can't
+          # dist-upgrade, this matters.
           - target: x86_64-unknown-linux-gnu
-            os: ubuntu-latest
+            os: ubuntu-22.04
             name: mhrv-rs-linux-amd64
           - target: aarch64-unknown-linux-gnu
-            os: ubuntu-latest
+            os: ubuntu-22.04
             name: mhrv-rs-linux-arm64
           - target: x86_64-apple-darwin
             os: macos-latest