feat: Add rebrand CI/CD workflows to main branch

- Add 72 rebrand workflow files (polkadot→pezkuwi, substrate→bizinikiwi, cumulus→pezcumulus)
- Add GitHub actions, issue templates, and configs
- Removed unnecessary workflows (fork-sync, gitspiegel, upstream-tracker, sync-templates, backport)
- Renamed zombienet test files to match new naming convention

.github/dependabot.yml

@@ -0,0 +1,31 @@
+version: 2
+updates:
+  # Update github actions:
+  - package-ecosystem: github-actions
+    directory: '/'
+    labels: ["A1-insubstantial", "R0-no-crate-publish-required"]
+    schedule:
+      interval: weekly
+    groups:
+      ci_dependencies:
+        patterns:
+        - "*"
+  # Update Rust dependencies:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    labels: ["A1-insubstantial", "R0-no-crate-publish-required"]
+    schedule:
+      interval: "weekly"
+    groups:
+      # We assume these crates to be semver abiding and can therefore group them together.
+      known_good_semver:
+        patterns:
+        - "syn"
+        - "quote"
+        - "log"
+        - "paste"
+        - "*serde*"
+        - "clap"
+        update-types:
+        - "minor"
+        - "patch"