ci: add Dependabot config and issue templates

Add weekly Dependabot updates for pip, Docker, and GitHub Actions.
Add issue templates for bug reports, feature requests, documentation,
and general feedback.

.github/dependabot.yml

@@ -0,0 +1,33 @@
+# Dependabot version updates
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+
+  # Python dependencies — requirements.txt
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    labels:
+      - "dependencies"
+
+  # Docker base image — Dockerfile
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    labels:
+      - "dependencies"
+
+  # GitHub Actions workflow dependencies
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+    labels:
+      - "dependencies"
+      - "ci"