i18n(cs): translate the eleven strings added on main

Main added eleven strings since the last merge: History's Clear History
and Delete Redoable Actions with its confirmation, the work area's
Start/End/Duration readouts and Work Area Bar, Transparency Grid, Show
Duplicate Frame Markers, and the AV1 and H.265 hardware-encoder
messages. Czech again has every Spanish source key plus `1/2` (3,608).

- History entries are "akce", the greyed-out ones "zašedlé".
- Encoder is "kodér", as in the existing export rows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/localization-parity.md

@@ -54,7 +54,7 @@ whole interface, one PR) at ~4–8 h per language for the catalog plus tests.
 | Korean | ko | 3,573 (same entries as Spanish, plus the macOS Settings item) | as Spanish | installed system Hangul font (Malgun Gothic, Apple SD Gothic Neo, Noto Sans CJK KR…); refused without one | not recorded; welcome | partial (#508) | review; Hangul in craft-fonts for the web |
 | Vietnamese | vi | 0 (0%) | — | Latin with stacked diacritics (font coverage to check) | — | none | 6–12 h + review |
 | *Other shipped:* Italian | it | 3,573 (same entries as Spanish, plus the macOS Settings item) | as Spanish | Latin (bundled fonts) | not recorded; welcome | partial | review |
-| Czech | cs | 3,597 (all Spanish source keys, plus the playback-resolution label `1/2`) | dialogs, Settings, effects, shortcuts, status; engine errors English | Latin (bundled fonts) | not reviewed | partial | native review |
+| Czech | cs | 3,608 (all Spanish source keys, plus the playback-resolution label `1/2`) | dialogs, Settings, effects, shortcuts, status; engine errors English | Latin (bundled fonts) | not reviewed | partial | native review |
 | *Other shipped:* Ukrainian | uk | 351 (10.0%) | menus only | Cyrillic (bundled) | not recorded | menus only | 5–9 h |
 
 UI strings are catalog entries (the non-comment lines of `src/i18n/<code>.tsv`; English counts the