feat(notes): raise annotation text limit from 10,000 to 100,000 chars

The 10k validator cap rejected legitimate long-form notes — a
scholarly reading note with quoted passages and footnotes lands
around 10.1k chars and failed at save with the raw validator error.

Raise the cap to 100,000 on all six annotation text fields in the
media handler request structs:

- CreateMediaNoteRequest / UpdateMediaNoteRequest Content
- CreateMediaHighlightRequest / UpdateMediaHighlightRequest NoteText
- CreateMediaBookmarkRequest / UpdateMediaBookmarkRequest Notes

No other layer changes: the media_notes / media_highlights columns
are unbounded TEXT, and the KOReader + websocket sync paths never
had a length cap, so the REST API now matches the rest of the
system instead of being the strictest gate.

New integration test pins the boundary: 50k and 100k-char notes
return 201, 100,001 chars returns 400.

cmd/server/tests/media_note_length_test.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestMediaNoteLengthLimits verifies the note content validator cap
+// (internal/handlers/media.go): content up to 100,000 chars is accepted,
+// longer content is rejected with 400.
+func TestMediaNoteLengthLimits(t *testing.T) {
+	setup := setupTestServer(t)
+
+	token := setup.Token
+	mediaItemID := createTestMediaItemID(t, setup)
+
+	postNote := func(content string) int {
+		payload := map[string]interface{}{
+			"content":  content,
+			"position": "page:1",
+		}
+		body, _ := json.Marshal(payload)
+		req, _ := http.NewRequest("POST", setup.Server.URL+"/api/media-items/"+mediaItemID+"/notes", bytes.NewBuffer(body))
+		req.Header.Set("Content-Type", "application/json")
+		req.Header.Set("Authorization", "Bearer "+token)
+
+		client := &http.Client{}
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		defer func(Body io.ReadCloser) {
+			_ = Body.Close()
+		}(resp.Body)
+		return resp.StatusCode
+	}
+
+	t.Run("50k-char note accepted", func(t *testing.T) {
+		assert.Equal(t, http.StatusCreated, postNote(strings.Repeat("a", 50000)))
+	})
+
+	t.Run("100k-char note accepted at boundary", func(t *testing.T) {
+		assert.Equal(t, http.StatusCreated, postNote(strings.Repeat("b", 100000)))
+	})
+
+	t.Run("over-limit note rejected", func(t *testing.T) {
+		assert.Equal(t, http.StatusBadRequest, postNote(strings.Repeat("c", 100001)))
+	})
+}

internal/handlers/media.go

@@ -102,13 +102,13 @@ type UpdateMediaItemRequest struct {
 
 // CreateMediaNoteRequest represents the request for creating a media note
 type CreateMediaNoteRequest struct {
-	Content  string `json:"content" validate:"required,min=1,max=10000"`
+	Content  string `json:"content" validate:"required,min=1,max=100000"`
 	Position string `json:"position"`
 }
 
 // UpdateMediaNoteRequest represents the request for updating a media note
 type UpdateMediaNoteRequest struct {
-	Content  string `json:"content" validate:"required,min=1,max=10000"`
+	Content  string `json:"content" validate:"required,min=1,max=100000"`
 	Position string `json:"position"`
 }
 
@@ -120,7 +120,7 @@ type CreateMediaHighlightRequest struct {
 	EpubcfiStart     string  `json:"epubcfi_start" validate:"max=2000"`
 	EpubcfiEnd       string  `json:"epubcfi_end" validate:"max=2000"`
 	Color            string  `json:"color" validate:"omitempty,len=7"`
-	NoteText         string  `json:"note_text" validate:"max=10000"`
+	NoteText         string  `json:"note_text" validate:"max=100000"`
 	NoteID           string  `json:"note_id"`
 	PercentageStart  float64 `json:"percentage_start"`
 	PercentageEnd    float64 `json:"percentage_end"`
@@ -135,7 +135,7 @@ type UpdateMediaHighlightRequest struct {
 	EpubcfiStart     string  `json:"epubcfi_start" validate:"max=2000"`
 	EpubcfiEnd       string  `json:"epubcfi_end" validate:"max=2000"`
 	Color            string  `json:"color" validate:"omitempty,len=7"`
-	NoteText         string  `json:"note_text" validate:"max=10000"`
+	NoteText         string  `json:"note_text" validate:"max=100000"`
 	NoteID           string  `json:"note_id"`
 	PercentageStart  float64 `json:"percentage_start"`
 	PercentageEnd    float64 `json:"percentage_end"`
@@ -146,7 +146,7 @@ type UpdateMediaHighlightRequest struct {
 type CreateMediaBookmarkRequest struct {
 	Title            string  `json:"title" validate:"required,min=1,max=255"`
 	Position         string  `json:"position" validate:"max=100"`
-	Notes            string  `json:"notes" validate:"max=10000"`
+	Notes            string  `json:"notes" validate:"max=100000"`
 	CfiPosition      string  `json:"cfi_position" validate:"max=255"`
 	PageNumber       int32   `json:"page_number"`
 	ChapterNumber    int32   `json:"chapter_number"`
@@ -160,7 +160,7 @@ type CreateMediaBookmarkRequest struct {
 // UpdateMediaBookmarkRequest represents the request for updating a media bookmark
 type UpdateMediaBookmarkRequest struct {
 	Title    string `json:"title" validate:"required,min=1,max=255"`
-	Notes    string `json:"notes" validate:"max=10000"`
+	Notes    string `json:"notes" validate:"max=100000"`
 	Position string `json:"position" validate:"max=100"`
 }