refactor: changed effects, add shell completions

- Extract all apply_* effect methods from screenshot.rs into dedicated
  src/effects.rs (blur, vignette, pixelate, swirl) — screenshot.rs
- Rewrite apply_blur: replace broken fastblur::gaussian_blur (horizontal-
  only box blur, backbuf dropped) with correct inline two-pass sliding-
  window box blur operating directly on Cairo surface bytes — ~10×
  faster, no ImageBuffer round-trip, no fastblur dependency
- Remove melting effect entirely (seems to be hard to implement
  properely, tried multiple itterations)
- Drop unused dependencies: fastblur, rand
- Add clap_complete dependency + --completions {bash,fish,zsh} flag,
  with CompletionShell enum in config.rs
- Fix show_* flags defaulting to true: remove default_value_t=true from
  show_media, show_battery, show_network, show_bluetooth, show_album_art,
  show_caps_lock_text — all now opt-in (matching user expectation)
- Convert peek toggle to hold: toggle_peek() → set_peek_held(held: bool),
  Press calls set_peek_held(true), new Release handler iterates all
  surfaces and calls set_peek_held(false), matching Ctrl-hold behavior
- Fix cursor rendering: increase font size 11→14 for peeked chars,
  handle cursor_position == 0 (prevent negative t wrapping to far ring
  end)
- Fix peek hit-test: use shape-aware point_in_shape() instead of simple
  circle pill/square/diamond/hexagon now detect clicks correctly within
  their area
- Remove per-frame DEBUG logs: PEEK/DOT mode in lock.rs,
  set_password_display/peek_password in render/mod.rs
- Update README: embed rustlock-effects.webp demo, remove melting
  references, correct show_* defaults and options table

.github/workflows/security.yml

@@ -11,6 +11,14 @@ on:
       - 'Cargo.lock'
       - 'deny.toml'
       - '.github/workflows/security.yml'
+  pull_request:
+    branches: [main, master]
+    paths:
+      - 'Cargo.toml'
+      - 'Cargo.lock'
+      - 'deny.toml'
+      - '.github/workflows/security.yml'
+    types: [opened, synchronize, reopened]
 
 env:
   CARGO_TERM_COLOR: always
@@ -19,7 +27,7 @@ jobs:
   security-audit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
 
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable