Replace PowerShell release script with bash

The release script no longer publishes to NuGet directly. Instead,
publishing is handled by the release.yml GitHub Actions workflow
using trusted publishing.

Also adds plan.md with manual setup instructions for the GitHub
environment and NuGet.org trusted publishing policy.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: oschwald

README.dev.md

@@ -1,4 +1,6 @@
-To publish the to NuGet:
+## Releasing
 
-1. Update release notes.
-2. Run `.\dev-bin\release.ps1`.
+1. Create a release branch from main.
+2. Update `releasenotes.md` with the version and today's date.
+3. Run `./dev-bin/release.sh`.
+4. Approve the release in the GitHub Actions workflow (requires `nuget` environment approval).

dev-bin/release.ps1

@@ -0,0 +1,68 @@
+#!/bin/bash
+
+set -eu -o pipefail
+
+# Check that we're not on the main branch
+current_branch=$(git branch --show-current)
+if [ "$current_branch" = "main" ]; then
+    echo "Error: Releases should not be done directly on the main branch."
+    echo "Please create a release branch and run this script from there."
+    exit 1
+fi
+
+# Fetch latest changes and check that we're not behind origin/main
+echo "Fetching from origin..."
+git fetch origin
+
+if ! git merge-base --is-ancestor origin/main HEAD; then
+    echo "Error: Current branch is behind origin/main."
+    echo "Please merge or rebase with origin/main before releasing."
+    exit 1
+fi
+
+changelog=$(cat releasenotes.md)
+
+regex='([0-9]+\.[0-9]+\.[0-9]+(-[a-zA-Z0-9]+)?) \(([0-9]{4}-[0-9]{2}-[0-9]{2})\)'
+
+if [[ ! $changelog =~ $regex ]]; then
+    echo "Could not find version/date in releasenotes.md!"
+    exit 1
+fi
+
+version="${BASH_REMATCH[1]}"
+date="${BASH_REMATCH[3]}"
+
+if [[ "$date" != "$(date +"%Y-%m-%d")" ]]; then
+    echo "$date is not today!"
+    exit 1
+fi
+
+tag="v$version"
+
+if [ -n "$(git status --porcelain)" ]; then
+    echo ". is not clean." >&2
+    exit 1
+fi
+
+# Update version in csproj
+sed -i "s|<VersionPrefix>[^<]*</VersionPrefix>|<VersionPrefix>$version</VersionPrefix>|" MaxMind.Db/MaxMind.Db.csproj
+
+# Build and test
+dotnet build -c Release
+dotnet test -c Release
+
+echo $'\nDiff:'
+git diff
+
+read -e -p "Commit changes and create release? (y/n) " should_continue
+
+if [ "$should_continue" != "y" ]; then
+    echo "Aborting"
+    exit 1
+fi
+
+git commit -m "Prepare for $version" -a
+
+git push
+
+gh release create --target "$(git branch --show-current)" -t "$version" "$tag"