refactor: remove dead code across server, templ pages, and client modules

Deadcode-verified removals (RTA reachability from main, cross-checked
with -test and textual xrefs):

Go server:
- whole files: middleware/transaction.go, middleware/error_handler.go,
  middleware/password_validator.go (live registration machinery kept),
  handlers/sync.go, sync/offline.go
- unrouted endpoints: auth UpdateUsername/UpdateEmail, timezone
  settings handler, OPDS RegisterOPDS, Kobo LibrarySync handler,
  ReaderHandler.ShowReader, JSON-data twins on collections/library
- duplicate book-matching handlers (book_matching.go Handler twins,
  matching.go MatchingHandler twins), superseded helpers
  (router.parseUUID, handlers.ValidateDeviceToken, normalizePath,
  userExists, generateLockID)

Templ/client:
- never-routed pages: api_explorer.templ, queue.templ and their
  client modules api-explorer.ts, api-explorer-docs.ts, queue.ts
- fully orphaned wrapper modules events.ts, dom.ts
- broken clearSyncQueue (called a nonexistent endpoint) and the
  hidden, never-populated sync-queue section on the devices page
- 166+ unused exports demoted to private (knip-verified); ~85 truly
  dead declarations removed via tsc noUnusedLocals fixpoint
- stale 'interactive API Explorer' claims dropped from docs

The docs drift-gate package (internal/docs), templ-bound modules
(dashboard, stats, header, index, login, profile*, bookshelf,
collections, toast-error), sqlc-generated code, and web/static are
intentionally untouched.

internal/sync/cfi_converter.go

@@ -967,45 +967,6 @@ func findNodeAtCharOffset(root *html.Node, targetOffset int) (*html.Node, int) {
 	return found, currentOffset
 }
 
-func (c *CFIConverter) computePercentage(xp *CREXPointer, target *html.Node, remainingOffset int) float64 {
-	spine, err := c.loadSpine()
-	if err != nil {
-		return -1
-	}
-
-	charOffset := 0
-	for i := 1; i < xp.FragmentIndex; i++ {
-		doc, _, err := c.getContentDoc(i)
-		if err != nil {
-			continue
-		}
-		body := findBody(doc)
-		if body != nil {
-			charOffset += countTextChars(body)
-		}
-	}
-
-	charOffset += countTextCharsBefore(target)
-	charOffset += remainingOffset
-
-	totalChars := int64(0)
-	for i := range spine.items {
-		doc, _, err := c.getContentDoc(i + 1)
-		if err != nil {
-			continue
-		}
-		body := findBody(doc)
-		if body != nil {
-			totalChars += int64(countTextChars(body))
-		}
-	}
-
-	if totalChars <= 0 {
-		return -1
-	}
-	return float64(charOffset) / float64(totalChars)
-}
-
 type indexedNode struct {
 	node      *html.Node
 	textChunk []*html.Node
@@ -1157,7 +1118,6 @@ func findTextChunk(parent *html.Node, textNode *html.Node) (int, int, string) {
 	return -1, 0, ""
 }
 
-
 func findElementCFIIndex(parent *html.Node, element *html.Node) int {
 	indexed := indexChildNodes(parent)
 	for i, node := range indexed {

internal/sync/cfi_repro_clean_test.go

@@ -11,8 +11,8 @@ package sync
 // cfi_verify_manual_test.go.
 
 import (
-	"fmt"
 	"encoding/json"
+	"fmt"
 	"os"
 	"strings"
 	"testing"

internal/sync/cfi_verify_test.go

@@ -7,8 +7,10 @@ import (
 
 // The fixture (writeTestEPUB in cfi_converter_test.go): 6 spine docs.
 // doc2 = spine index 1 with two paragraphs:
-//   p1: "The family of Dashwood had long been settled in Sussex."
-//   p2: "Their estate was large, and their residence was at Norland Park."
+//
+//	p1: "The family of Dashwood had long been settled in Sussex."
+//	p2: "Their estate was large, and their residence was at Norland Park."
+//
 // Hand-derived local paths (html→body /4, body→div /4, div→p /4|/6,
 // p→text chunk /1):
 const (

internal/sync/kepub_cfi_converter.go

@@ -1,7 +1,6 @@
 package sync
 
 import (
-	"fmt"
 	"log"
 
 	"golang.org/x/net/html"
@@ -13,10 +12,10 @@ type KEPUBCFIConverter struct {
 }
 
 type KEPUBConversionResult struct {
-	CFI               string
-	ExtractedContext  string
-	Percentage        float64
-	Precision         string
+	CFI              string
+	ExtractedContext string
+	Percentage       float64
+	Precision        string
 }
 
 func NewKEPUBCFIConverter(epubPath, kepubPath string) *KEPUBCFIConverter {
@@ -265,57 +264,6 @@ func extractSurroundingText(textNode *html.Node, offset int, window int) string
 	return normalizeWhitespace(string(allRunes[start:end]))
 }
 
-func (k *KEPUBCFIConverter) ComputeKEPUBPercentage(kepubCFI string) (float64, error) {
-	if !IsStandardEPUBCFI(kepubCFI) {
-		return -1, fmt.Errorf("not a standard epubcfi")
-	}
-
-	spineIndex, steps, err := parseEPUBCFI(kepubCFI)
-	if err != nil {
-		return -1, err
-	}
-
-	kepubDoc, _, docErr := k.kepubConverter.getContentDoc(spineIndex + 1)
-	if docErr != nil {
-		return -1, docErr
-	}
-
-	kepubBody := findBody(kepubDoc)
-	if kepubBody == nil {
-		return -1, fmt.Errorf("no body in kepub doc")
-	}
-
-	textNode, textOffset, resolveErr := resolveCFIToNode(kepubBody, steps)
-	if resolveErr != nil {
-		return -1, resolveErr
-	}
-
-	charOffset := countTextCharsBefore(textNode) + textOffset
-
-	total := 0
-	kepubSpine, spineErr := k.kepubConverter.loadSpine()
-	if spineErr != nil {
-		return -1, spineErr
-	}
-
-	for i := range kepubSpine.items {
-		doc, _, dErr := k.kepubConverter.getContentDoc(i + 1)
-		if dErr != nil {
-			continue
-		}
-		b := findBody(doc)
-		if b != nil {
-			total += countTextChars(b)
-		}
-	}
-
-	if total <= 0 {
-		return -1, fmt.Errorf("no text in kepub")
-	}
-
-	return float64(charOffset) / float64(total), nil
-}
-
 func init() {
 	_ = log.Printf
 }

internal/sync/progress.go

@@ -260,21 +260,6 @@ func FormatProgressForDisplay(formatGroup FormatGroup, progress map[string]inter
 	}
 }
 
-// ParseProgressFromJSON parses progress data from JSON
-func ParseProgressFromJSON(data []byte) (*ProgressData, error) {
-	var progress ProgressData
-	err := json.Unmarshal(data, &progress)
-	if err != nil {
-		return nil, err
-	}
-	return &progress, nil
-}
-
-// MarshalProgressToJSON converts progress data to JSON
-func MarshalProgressToJSON(progress *ProgressData) ([]byte, error) {
-	return json.Marshal(progress)
-}
-
 const CharsPerPage int64 = 1800
 
 func EstimatedPages(totalCharacters int64) int {