Add Forgejo template variable expansion for automatic repo customization

Replace hardcoded TODO markers with Forgejo template variables (${REPO_NAME},
${REPO_OWNER}, etc.) so new repos created from this template are auto-customized.
Use Forgejo Actions context variables in build.yaml for dynamic FORGE_URL.
Hardcode forge.eblu.me as the Forgejo instance. Update CLAUDE.md and README.md
to reflect reduced manual setup steps.

Python class names kept as manual TODO (same as directory rename) since template
variables in Python code positions aren't valid syntax for linters.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/changelog.d/feature-forgejo-template-variables.infra.md

@@ -0,0 +1 @@
+Add Forgejo template repository variable expansion — most TODO markers are now auto-resolved when creating a new repo from this template.

docs/index.md

@@ -7,9 +7,7 @@ tags:
 
 # Project Documentation
 
-<!-- TODO: Fill in project description when forking this template -->
-
-Welcome to the **PROJECT_NAME** documentation.
+Welcome to the **${REPO_NAME}** documentation.
 
 ## Navigation
 

docs/quartz.config.ts

@@ -7,7 +7,7 @@ import * as Plugin from "./quartz/plugins"
  */
 const config: QuartzConfig = {
   configuration: {
-    pageTitle: "Project Docs", // TODO: Update to your project name
+    pageTitle: "${REPO_NAME_TITLE} Docs",
     pageTitleSuffix: "",
     enableSPA: true,
     enablePopovers: true,

docs/quartz.layout.ts

@@ -13,7 +13,7 @@ export const sharedPageComponents: SharedLayout = {
   afterBody: [],
   footer: Component.Footer({
     links: {
-      "Repository": "https://CHANGEME.example.com/owner/repo", // TODO: Update to your repo URL
+      "Repository": "${REPO_LINK}",
     },
   }),
 }