chore(community): rewards program, issue templates, and triage workflow (#176)

* chore(community): rewards program, issue templates, and triage workflow

Adds the public-facing community engagement infrastructure.

CONTRIBUTING.md introduces a three-tier rewards program (sticker / t-shirt /
hoodie) gated on merged PRs, with explicit eligibility rules to keep the
program sustainable. Fulfillment is handled by emailing support@kaelio.com.

The .github/ISSUE_TEMPLATE/ forms give structure to bug reports and feature
requests, and config.yml routes questions to the KTX Slack instead of GitHub
Discussions (matching the routing established in docs-site/.../support.mdx).

The triage-issues workflow applies a needs-triage label only when the issue
author isn't OWNER, MEMBER, or COLLABORATOR — so internal issues stay clean
while external contributions get queued for maintainer review.

The first 14 connector contribution issues (#161-174) have been filed using
these labels and reward tiers.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore(community): add SECURITY.md

Documents the private reporting channel (GitHub Security Advisories with
support@kaelio.com as fallback), what reporters should include, and the
supported-version policy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/triage-issues.yml

@@ -0,0 +1,28 @@
+name: Triage new issues
+
+on:
+  issues:
+    types: [opened]
+
+permissions:
+  issues: write
+
+jobs:
+  label-external:
+    name: Add needs-triage to external issues
+    runs-on: ubuntu-latest
+    if: |
+      github.event.issue.author_association != 'OWNER' &&
+      github.event.issue.author_association != 'MEMBER' &&
+      github.event.issue.author_association != 'COLLABORATOR'
+    steps:
+      - name: Apply needs-triage label
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.issues.addLabels({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              labels: ['needs-triage'],
+            });