Add accent-insensitive search option

[yyyyyyyan]

Make search accent-insensitive by default: both the search term and
entry field values are normalized by decomposing to Unicode NFD and
stripping combining marks, so that e.g. "pouzivatel" matches "používateľ"
and vice versa.

The + (exact match) modifier implicitly forces accent-sensitive matching
per-term, giving users fine-grained control without a separate UI toggle.
For example, +café matches only "café" and not "cafe".

AI Disclosure: This PR was developed with assistance from Claude (Opus 4.6). I created an implementation plan in an interactive session with Claude, and Claude executed the initial implementation. After my review and tests I manually refined the code (added ASCII fast path, added some edge-case unit tests, fixed signal/multiplexer race condition in db open sequence).

Fixes #6181

Screenshots

Accent-insensitive search (default): "testingabc" matches accented entry "téstîñgàbç":

Exact match (+) forces accent-sensitive: "+testingabc" does not match accented entry:

Exact match (+) with accented query: "+téstîñgàbç" matches the accented entry:

Testing strategy

• Added testAccentInsensitiveSearch to TestEntrySearcher covering:
  • ASCII query matching accented entry and vice versa
  • Field-specific search with accent folding (title:, attachment:, tag:, group:)
  • Exact match (+) forces accent-sensitive, exclude (!) works with folding
  • Case-sensitive combined with accent-insensitive
• All existing tests pass unchanged
• Manual testing with KeePassXC GUI

Type of change

• ✅ New feature (change that adds functionality)

[yyyyyyyan]

A couple of things I'd like to get input on:

1. 60f6259 fixes a bug where EntrySearcher was always constructed with hardcoded defaults, ignoring the user's saved config. I believe this went undetected because all existing toggle defaults were false, matching the constructor defaults, but I bumped into it with the new accentSensitive param defaulting to true. Not sure if this should stay here or be split into a separate issue/PR.

2. I went with accent-sensitive as the default (preserving current behavior), but honestly as a Brazilian Portuguese speaker I'd prefer accent-insensitive as the default. I'd like to know if anyone has any inputs regarding this.

[Copilot]

Pull request overview

Adds a user-facing search toggle to control accent/diacritics sensitivity in the KeePassXC GUI, wiring it through the existing SearchWidget → DatabaseWidget → EntrySearcher flow and implementing Unicode NFD + combining-mark stripping when accent-insensitive matching is enabled.

Changes:

• Add an “Accent sensitive” toggle to the search menu and persist it via a new GUI config key.
• Extend EntrySearcher to support accent-insensitive matching by stripping diacritics from both query terms and searched fields (with an ASCII fast path).
• Add unit tests covering accent-insensitive matching across fields/modifiers and interactions with case sensitivity.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/TestEntrySearcher.h	Adds a new test slot for accent-insensitive search.
tests/TestEntrySearcher.cpp	Introduces comprehensive coverage for accent-insensitive search behavior and modifiers.
src/gui/SearchWidget.h	Adds signal/slot and action member for the new toggle.
src/gui/SearchWidget.cpp	Adds the menu action, persists the setting, and emits the new policy signal on DB changes.
src/gui/DatabaseWidget.h	Adds a slot to apply the accent-sensitivity setting to searching.
src/gui/DatabaseWidget.cpp	Initializes EntrySearcher from config and applies updates via setSearchAccentSensitive().
src/core/Tools.h	Declares Tools::stripDiacritics() utility.
src/core/Tools.cpp	Implements diacritics stripping via NFD decomposition + combining-mark removal (ASCII fast path).
src/core/EntrySearcher.h	Extends constructor/state with accentSensitive and adds setters/getters.
src/core/EntrySearcher.cpp	Applies diacritics stripping to both parsed terms (regex source) and matched fields/lists.
src/core/Config.h	Adds new config key GUI_SearchAccentSensitive.
src/core/Config.cpp	Registers the new config key with default true (accent-sensitive).

[droidmonkey]

I am a fan of making the default more "liberal" and actually remove the option entirely. We already have an "exact match" prefix (ie, +t:acćent). If the user wants exact matching, accents are respected, otherwise the default is no accent matching.

[yyyyyyyan]

@droidmonkey done!

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

[Copilot]

SearchTerm::accentSensitive defaults to false when callers value-initialize SearchTerm{} (e.g. src/fdosecrets/objects/Collection.cpp:279), which makes programmatic searches silently become accent-insensitive. This changes existing behavior for callers that use EntrySearcher::search(const QList<SearchTerm>&, ...) and currently rely on exact (diacritic-sensitive) matching (notably Secret Service attribute matching built with EXACT_MATCH | CASE_SENSITIVE). Consider giving accentSensitive a default member initializer of true (so programmatic terms remain accent-sensitive unless explicitly overridden) while keeping parseSearchTerms() setting it based on the + modifier.

Suggested change

	bool accentSensitive;
	bool accentSensitive = true;

[yyyyyyyan]

@droidmonkey is anything needed on my end? Let me know if it needs any adjustments!!

[droidmonkey]

Nope you are gtg, I just need to manually test this to confirm functionality