E3: add community health files

The repository had no contributor-facing documentation or automation
config. Add the standard set:

- CHANGELOG.md (Keep a Changelog format, 0.1.0-0.1.4 plus Unreleased)
- CONTRIBUTING.md (build/test steps, change standards, PolyForm-NC note)
- SECURITY.md (private reporting, supported versions)
- CODE_OF_CONDUCT.md (Contributor Covenant 2.1)
- .github/ISSUE_TEMPLATE (bug report, feature request, config)
- .github/PULL_REQUEST_TEMPLATE.md
- .github/dependabot.yml (cargo, npm, pip, github-actions — the last
  keeps the D1 SHA pins current)
- .github/CODEOWNERS

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,31 @@
+---
+name: Feature request
+about: Suggest a new indicator or capability for Wickra
+title: "[feature] "
+labels: enhancement
+assignees: ""
+---
+
+## Problem
+
+<!-- What are you trying to do that Wickra cannot do today? -->
+
+## Proposed solution
+
+<!-- For a new indicator: its name, formula, and the standard parameters.
+     Link a reference implementation (TA-Lib, pandas-ta) if one exists. -->
+
+## Alternatives considered
+
+<!-- Other approaches and why they fall short. -->
+
+## Scope
+
+- [ ] Affects the Rust core
+- [ ] Should be exposed in the Python binding
+- [ ] Should be exposed in the Node binding
+- [ ] Should be exposed in the WASM binding
+
+## Additional context
+
+<!-- Anything else that helps. -->