Replace Python CLI with Gitea issue tracker setup

Switch from a custom CLI ticketing tool to Gitea-native issue tracking.
Add issue templates (bug, feature, task) and a curated initial backlog
of 20 tickets covering project foundation, testing, security, docs,
features, and community maintenance.

.gitea/ISSUE_TEMPLATE/task.md

@@ -0,0 +1,26 @@
+---
+name: "📋 Task / Epic"
+about: "Track a general task, investigation, or epic."
+title: "[Task] "
+labels: ["task"]
+assignees: []
+---
+
+## Summary
+
+<!-- One or two sentences describing the task. -->
+
+## Subtasks
+
+- [ ]
+- [ ]
+- [ ]
+
+## Dependencies
+
+<!-- Does this block or is it blocked by other issues? -->
+
+## Notes
+
+<!-- Links, design docs, or relevant context. -->
+