docs: add Versioning wiki page

Versioning.md

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+# Versioning
+
+Versions are managed entirely on the TeamCity side — **do not set `<Version>` in `.csproj` files**.
+
+## How it works
+
+At publish time, the TC `HrynCo / HrynCo.EF / publish` build:
+
+1. Writes the current build number into `Directory.Build.props` as `<Version>%build.number%</Version>`.
+2. Restores, builds, and packs both projects in Release configuration.
+3. Pushes the resulting `.nupkg` files to nuget.org.
+
+## Build number pattern
+
+The build number follows the pattern `1.0.<counter>` (e.g. `1.0.6`, `1.0.7`, …).
+The counter increments automatically on each successful publish run.
+
+## Releasing
+
+To release a new version: merge to `main` — the publish build triggers automatically on push to `main`.
+
+## Bumping major or minor version
+
+Update the build number pattern in TC:
+
+> **HrynCo → HrynCo.EF → publish → Edit Configuration → General → Build number format**
+
+Change `1.0.%build.counter%` to e.g. `2.0.%build.counter%`.