feat(server): implement FTS5-based full-text search (#5079)

* build: add sqlite_fts5 build tag to enable FTS5 support

* feat: add SearchBackend config option (default: fts)

* feat: add buildFTS5Query for safe FTS5 query preprocessing

* feat: add FTS5 search backend with config toggle, refactor legacy search

- Add searchExprFunc type and getSearchExpr() for backend selection
- Rename fullTextExpr to legacySearchExpr
- Add ftsSearchExpr using FTS5 MATCH subquery
- Update fullTextFilter in sql_restful.go to use configured backend

* feat: add FTS5 migration with virtual tables, triggers, and search_participants

Creates FTS5 virtual tables for media_file, album, and artist with
unicode61 tokenizer and diacritic folding. Adds search_participants
column, populates from JSON, and sets up INSERT/UPDATE/DELETE triggers.

* feat: populate search_participants in PostMapArgs for FTS5 indexing

* test: add FTS5 search integration tests

* fix: exclude FTS5 virtual tables from e2e DB restore

The restoreDB function iterates all tables in sqlite_master and
runs DELETE + INSERT to reset state. FTS5 contentless virtual tables
cannot be directly deleted from. Since triggers handle FTS5 sync
automatically, simply skip tables matching *_fts and *_fts_* patterns.

* build: add compile-time guard for sqlite_fts5 build tag

Same pattern as netgo: compilation fails with a clear error if
the sqlite_fts5 build tag is missing.

* build: add sqlite_fts5 tag to reflex dev server config

* build: extract GO_BUILD_TAGS variable in Makefile to avoid duplication

* fix: strip leading * from FTS5 queries to prevent "unknown special query" error

* feat: auto-append prefix wildcard to FTS5 search tokens for broader matching

Every plain search token now gets a trailing * appended (e.g., "love" becomes
"love*"), so searching for "love" also matches "lovelace", "lovely", etc.
Quoted phrases are preserved as exact matches without wildcards. Results are
ordered alphabetically by name/title, so shorter exact matches naturally
appear first.

* fix: clarify comments about FTS5 operator neutralization

The comments said "strip" but the code lowercases operators to
neutralize them (FTS5 operators are case-sensitive). Updated comments
to accurately describe the behavior.

* fix: use fmt.Sprintf for FTS5 phrase placeholders

The previous encoding used rune('0'+index) which silently breaks with
10+ quoted phrases. Use fmt.Sprintf for arbitrary index support.

* fix: validate and normalize SearchBackend config option

Normalize the value to lowercase and fall back to "fts" with a log
warning for unrecognized values. This prevents silent misconfiguration
from typos like "FTS", "Legacy", or "fts5".

* refactor: improve documentation for build tags and FTS5 requirements

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor: convert FTS5 query and search backend normalization tests to DescribeTable format

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: add sqlite_fts5 build tag to golangci configuration

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: add UISearchDebounceMs configuration option and update related components

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: fall back to legacy search when SearchFullString is enabled

FTS5 is token-based and cannot match substrings within words, so
getSearchExpr now returns legacySearchExpr when SearchFullString
is true, regardless of SearchBackend setting.

* fix: add sqlite_fts5 build tag to CI pipeline and Dockerfile

* fix: add WHEN clauses to FTS5 AFTER UPDATE triggers

Added WHEN clauses to the media_file_fts_au, album_fts_au, and
artist_fts_au triggers so they only fire when FTS-indexed columns
actually change. Previously, every row update (e.g., play count, rating,
starred status) triggered an unnecessary delete+insert cycle in the FTS
shadow tables. The WHEN clauses use IS NOT for NULL-safe comparison of
each indexed column, avoiding FTS index churn for non-indexed updates.

* feat: add SearchBackend configuration option to data and insights components

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: enhance input sanitization for FTS5 by stripping additional punctuation and special characters

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: add search_normalized column for punctuated name search (R.E.M., AC/DC)

Add index-time normalization and query-time single-letter collapsing to
fix FTS5 search for punctuated names. A new search_normalized column
stores concatenated forms of punctuated words (e.g., "R.E.M." → "REM",
"AC/DC" → "ACDC") and is indexed in FTS5 tables. At query time, runs of
consecutive single letters (from dot-stripping) are collapsed into OR
expressions like ("R E M" OR REM*) to match both the original tokens and
the normalized form. This enables searching by "R.E.M.", "REM", "AC/DC",
"ACDC", "A-ha", or "Aha" and finding the correct results.

* refactor: simplify isSingleUnicodeLetter to avoid []rune allocation

Use utf8.DecodeRuneInString to check for a single Unicode letter
instead of converting the entire string to a []rune slice.

* feat: define ftsSearchColumns for flexible FTS5 search column inclusion

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: update collapseSingleLetterRuns to return quoted phrases for abbreviations

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: implement extractPunctuatedWords to handle artist/album names with embedded punctuation

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: implement extractPunctuatedWords to handle artist/album names with embedded punctuation

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor: punctuated word handling to improve processing of artist/album names

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: add CJK support for search queries with LIKE filters

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: enhance FTS5 search by adding album version support and CJK handling

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor: search configuration to use structured options

Signed-off-by: Deluan <deluan@navidrome.org>

* feat: enhance search functionality to support punctuation-only queries and update related tests

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

Makefile

@@ -1,5 +1,6 @@
 GO_VERSION=$(shell grep "^go " go.mod | cut -f 2 -d ' ')
 NODE_VERSION=$(shell cat .nvmrc)
+GO_BUILD_TAGS=netgo,sqlite_fts5
 
 # Set global environment variables, required for most targets
 export CGO_CFLAGS_ALLOW=--define-prefix
@@ -46,12 +47,12 @@ stop: ##@Development Stop development servers (UI and backend)
 .PHONY: stop
 
 watch: ##@Development Start Go tests in watch mode (re-run when code changes)
-	go tool ginkgo watch -tags=netgo -notify ./...
+	go tool ginkgo watch -tags=$(GO_BUILD_TAGS) -notify ./...
 .PHONY: watch
 
 PKG ?= ./...
 test: ##@Development Run Go tests. Use PKG variable to specify packages to test, e.g. make test PKG=./server
-	go test -tags netgo $(PKG)
+	go test -tags $(GO_BUILD_TAGS) $(PKG)
 .PHONY: test
 
 test-ndpgen: ##@Development Run tests for ndpgen plugin
@@ -62,7 +63,7 @@ testall: test test-ndpgen test-i18n test-js ##@Development Run Go and JS tests
 .PHONY: testall
 
 test-race: ##@Development Run Go tests with race detector
-	go test -tags netgo -race -shuffle=on  $(PKG)
+	go test -tags $(GO_BUILD_TAGS) -race -shuffle=on  $(PKG)
 .PHONY: test-race
 
 test-js: ##@Development Run JS tests
@@ -108,7 +109,7 @@ format: ##@Development Format code
 .PHONY: format
 
 wire: check_go_env ##@Development Update Dependency Injection
-	go tool wire gen -tags=netgo ./...
+	go tool wire gen -tags=$(GO_BUILD_TAGS) ./...
 .PHONY: wire
 
 gen: check_go_env ##@Development Run go generate for code generation
@@ -144,14 +145,14 @@ setup-git: ##@Development Setup Git hooks (pre-commit and pre-push)
 .PHONY: setup-git
 
 build: check_go_env buildjs ##@Build Build the project
-	go build -ldflags="-X github.com/navidrome/navidrome/consts.gitSha=$(GIT_SHA) -X github.com/navidrome/navidrome/consts.gitTag=$(GIT_TAG)" -tags=netgo
+	go build -ldflags="-X github.com/navidrome/navidrome/consts.gitSha=$(GIT_SHA) -X github.com/navidrome/navidrome/consts.gitTag=$(GIT_TAG)" -tags=$(GO_BUILD_TAGS)
 .PHONY: build
 
 buildall: deprecated build
 .PHONY: buildall
 
 debug-build: check_go_env buildjs ##@Build Build the project (with remote debug on)
-	go build -gcflags="all=-N -l" -ldflags="-X github.com/navidrome/navidrome/consts.gitSha=$(GIT_SHA) -X github.com/navidrome/navidrome/consts.gitTag=$(GIT_TAG)" -tags=netgo
+	go build -gcflags="all=-N -l" -ldflags="-X github.com/navidrome/navidrome/consts.gitSha=$(GIT_SHA) -X github.com/navidrome/navidrome/consts.gitTag=$(GIT_TAG)" -tags=$(GO_BUILD_TAGS)
 .PHONY: debug-build
 
 buildjs: check_node_env ui/build/index.html ##@Build Build only frontend