fix(sonar): point at this repo's own SonarCloud project (#25)

## Summary

`sonar.projectKey` was `hyperpolymath_rsr-template-repo` — the template
repo's own key, copied verbatim when this repo was derived from it.
Points it at its own project instead. **`sonar.organization` is
unchanged.**

## Why now, and why keys before tokens

This repo has no `SONAR_TOKEN` secret, so the scan currently aborts at
authentication and submits nothing:

```
##[warning]Running this GitHub Action without SONAR_TOKEN is not recommended
ERROR Not authorized or project not found. Please check the 'SONAR_TOKEN' environment
      variable, the 'sonar.projectKey' and 'sonar.organization' properties, ...
```

So the wrong key is **latent, not actively corrupting anything**. But
the moment `SONAR_TOKEN` is added, this repo would start reporting its
analysis into `hyperpolymath_rsr-template-repo`, mixed in with every
other repo carrying the copied key. Fixing the key first means that
never happens.

Found in an estate-wide sweep of `sonar-project.properties` files
against the SonarCloud API. Same fix already merged in
hyperpolymath/systemet#20 and
hyperpolymath/rsr-julia-library-template-repo#16.

## Organisation

`hyperpolymath` is correct and unchanged here. The estate consolidates
SonarCloud under the single `hyperpolymath` organisation regardless of
GitHub org — settled in metadatastician/IDApTIK#42.

## Test plan
- [x] Only `sonar.projectKey` and the project URL in the header comment
change
- [x] `sonar.organization` untouched
- [ ] Owner to provision the project and add `SONAR_TOKEN` — the
workflow cannot pass without both, independent of this change

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

Author: hyperpolymath

sonar-project.properties

@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: MPL-2.0
 # SonarQube Cloud (SonarCloud) configuration.
-# Project: https://sonarcloud.io/project/overview?id=hyperpolymath_rsr-template-repo
+# Project: https://sonarcloud.io/project/overview?id=hyperpolymath_anytype
 # Requires the SONAR_TOKEN repository secret + a SonarCloud project (owner setup).
 sonar.organization=hyperpolymath
-sonar.projectKey=hyperpolymath_rsr-template-repo
+sonar.projectKey=hyperpolymath_anytype
 
 # Analysable surface = shell scripts + any JS/TS the template carries. Idris2,
 # Zig, Elixir and AffineScript have no SonarCloud analyser; vendored, generated,