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/security.yml

@@ -29,7 +29,7 @@ jobs:
       - name: Install security tools
         uses: taiki-e/install-action@v2
         with:
-          tool: cargo-audit,cargo-deny,cargo-cyclonedx,cargo-outdated
+          tool: cargo-audit,cargo-deny,cargo-outdated
 
       - name: Run cargo audit
         run: cargo audit
@@ -37,15 +37,6 @@ jobs:
       - name: Run cargo deny
         run: cargo deny check
 
-      - name: Generate Software Bill of Materials (SBOM)
-        run: cargo cyclonedx --format json --override-filename bom
-
-      - name: Upload SBOM
-        uses: actions/upload-artifact@v7
-        with:
-          name: sbom
-          path: bom.json
-
       - name: Check for outdated dependencies
         run: cargo outdated --exit-code 1 || echo "Some dependencies are outdated"