feat: Add Czech translation (cs)

[Howardzi-nn]

Hello, awesome project!!
I tried to add the Czech language without any further intervention.

I was based on commit 0fa7e8d feat: Add French translation (fr) (#139) and ddf251e (Spanish)

Summary by CodeRabbit

• New Features
  • Added Czech as a supported language throughout the app.
  • Introduced Czech translations for the full interface, including common actions, validation, calendar, sharing, sync, and account-related screens.
  • Updated language lists in supported locales and documentation to include Czech.

[coderabbitai]

📝 Walkthrough

Walkthrough

Czech (cs) is added as a supported locale. lib/locales.ts registers the date-fns cs import and expands the locales tuple, Locale type, and dateFnsLocales mapping. A new messages/cs.json provides 819 lines of Czech translations. All existing locale files (de, en, es, fr, it) add the language.cs label, and the README features table is updated.

Czech Locale Addition

Layer / File(s)	Summary
Locale registration and Czech message catalog lib/locales.ts, messages/cs.json	Adds date-fns cs import, expands locales tuple and Locale type, adds cs to dateFnsLocales, and introduces the full Czech translation catalog covering all UI namespaces.
Czech language label in existing locale files and README messages/en.json, messages/de.json, messages/es.json, messages/fr.json, messages/it.json, README.md	Adds the language.cs key to all five existing locale files and updates the README features table to list Czech.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• panteLx/BetterShift#43: Introduced the locales/dateFnsLocales infrastructure in lib/locales.ts that this PR extends to add cs.
• panteLx/BetterShift#129: Added Spanish locale using the same pattern — expanding lib/locales.ts and adding language labels across messages/*.
• panteLx/BetterShift#139: Added French locale via the identical approach of updating lib/locales.ts, messages/* language labels, and the README.

Suggested labels

enhancement

Suggested reviewers

• panteLx

🐇 Hop hop, a new tongue joins the crew,
Czech words now dancing, shiny and new!
From calendar shifts to admin delight,
Each message in Czech is translated right.
The rabbit cheers: "Výborně!" — hooray! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately summarizes the main change: adding Czech translation support (cs).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

messages/cs.json (1)

816-817: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Fix inconsistent ICU plural style.

Lines 816–817 use the one/few/other categories, while the rest of this file uses explicit =0/=1/few/other. Standardize on one style for maintainability. Prefer the =0/=1/few/other pattern already used elsewhere in this file since it handles Czech's complex plural rules more explicitly.

♻️ Proposed fix

-    "deleteSelectedLogsDescription": "Smazat {count, plural, one {# vybraný protokol} few {# vybrané protokoly} other {# vybraných protokolů}}. Tuto akci nelze vrátit zpět.",
-    "willDeleteSelectedLogs": "{count, plural, one {# protokol} few {# protokoly} other {# protokolů}} bude trvale smazáno"
+    "deleteSelectedLogsDescription": "Smazat {count, plural, =0 {vybrané protokoly} =1 {1 vybraný protokol} few {# vybrané protokoly} other {# vybraných protokolů}}. Tuto akci nelze vrátit zpět.",
+    "willDeleteSelectedLogs": "{count, plural, =0 {Žádné protokoly} =1 {1 protokol} few {# protokoly} other {# protokolů}} bude trvale smazáno"

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@messages/cs.json` around lines 816 - 817, The ICU plural forms in the
`deleteSelectedLogsDescription` and `willDeleteSelectedLogs` messages are
inconsistent with the rest of `messages/cs.json`; update these entries to use
the same explicit `=0`/`=1`/`few`/`other` pattern used elsewhere in the file.
Make the change in the two affected message keys so the Czech plural handling
stays uniform and easy to maintain.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@messages/cs.json`:
- Around line 816-817: The ICU plural forms in the
`deleteSelectedLogsDescription` and `willDeleteSelectedLogs` messages are
inconsistent with the rest of `messages/cs.json`; update these entries to use
the same explicit `=0`/`=1`/`few`/`other` pattern used elsewhere in the file.
Make the change in the two affected message keys so the Czech plural handling
stays uniform and easy to maintain.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 14f59b7c-42e4-40c5-8951-16d6dccdbb80

📥 Commits

Reviewing files that changed from the base of the PR and between 1b0dd49 and 764dac7.

📒 Files selected for processing (8)

• README.md
• lib/locales.ts
• messages/cs.json
• messages/de.json
• messages/en.json
• messages/es.json
• messages/fr.json
• messages/it.json