feat: ring shapes, auth reuse, input tests, README docs, CI improvements

- Add --ring-shape (circle/square/diamond/hexagon/pill) with geometry module
- Reuse PAM context across auth attempts (no reload per-keystroke)
- Proper error propagation in screenshot effects (unwrap → Result + context)
- Remove theme presets (modern/pixel/glass) and --theme flag
- Add input cooldown after failed attempt (400ms debounce)
- Add Ctrl+held peek password, Home/End/Delete cursor keys
- Add all input unit tests (23 new tests)
- Add --max-dots, feedback duration, timeout, interval config options
- Add --log-path, --auth-timeout, verifying_color config fields
- Remove unused deps: futures, gio, env_logger, num-traits, thiserror, bytemuck
- Fix media bar: remove stop button, fix art+text overlap, uniform hit areas
- Fix CI: source-only releases, nightly prereleases, dependabot groups, labeler paths
- Update issue templates with structured forms
- Add stale workflow for inactive issues/PRs
- Update README: full options table (28 flags), remove theme docs, add shapes

.github/workflows/stale.yml

@@ -0,0 +1,26 @@
+name: Stale Issues and PRs
+
+on:
+  schedule:
+    - cron: '0 0 * * *'  # Daily
+  workflow_dispatch:
+
+jobs:
+  stale:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/stale@v9
+        with:
+          stale-issue-message: 'This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs within 7 days.'
+          stale-pr-message: 'This PR has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs within 7 days.'
+          close-issue-message: 'This issue has been automatically closed due to inactivity.'
+          close-pr-message: 'This PR has been automatically closed due to inactivity.'
+          days-before-stale: 30
+          days-before-close: 7
+          stale-issue-label: 'stale'
+          stale-pr-label: 'stale'
+          exempt-issue-labels: 'enhancement,security'
+          exempt-pr-labels: 'security,work-in-progress'