fix(renovate): align depName with actual repository name "ah-annotations"

Update README examples and renovate customManagers to reference
"ah-annotations" (with trailing 's') matching the repository name on
git.cryptic.systems.

Co-authored-by: Copilot <copilot@github.com>

README.md

@@ -17,7 +17,7 @@ steps:
   - uses: actions/checkout@v4
     with:
       fetch-depth: 0
-  - uses: volker.raschek/ah-annotation@v1
+  - uses: volker.raschek/ah-annotations@v1
 ```
 
 ### Explicit tags
@@ -29,7 +29,7 @@ steps:
   - uses: actions/checkout@v4
     with:
       fetch-depth: 0
-  - uses: volker.raschek/ah-annotation@v1.0.0
+  - uses: volker.raschek/ah-annotations@v1.0.0
     with:
       old-tag: v1.0.0
       new-tag: v2.0.0

renovate.json

@@ -13,10 +13,10 @@
         "^README\\.md$"
       ],
       "matchStrings": [
-        "uses: volker\\.raschek/ah-annotation@(?<currentValue>[^\\s\"']+)"
+        "uses: volker\\.raschek/ah-annotations@(?<currentValue>[^\\s\"']+)"
       ],
-      "depNameTemplate": "volker.raschek/ah-annotation",
+      "depNameTemplate": "volker.raschek/ah-annotations",
-      "packageNameTemplate": "https://git.cryptic.systems/volker.raschek/ah-annotation",
+      "packageNameTemplate": "https://git.cryptic.systems/volker.raschek/ah-annotations",
       "datasourceTemplate": "git-tags",
       "versioningTemplate": "semver"
     },
@@ -41,7 +41,7 @@
       ],
       "automerge": true,
       "matchDepNames": [
-        "volker.raschek/ah-annotation"
+        "volker.raschek/ah-annotations"
       ],
       "matchUpdateTypes": [
         "major",