fix(kon): security audit fixes — CSP, XSS, unwraps, key rename

Security fixes from code audit:
- CSP re-enabled in tauri.conf.json with strict directives
  (was null — critical vulnerability)
- XSS fix in viewer highlightText(): HTML entities escaped before
  inserting <mark> tags via {@html}
- Removed 3 unwrap() calls in rule_based.rs British English conversion
  — replaced with safe let-else guards
- Removed unwrap() on main window lookup in lib.rs setup — now uses
  if-let for graceful handling
- Wrapped JSON.parse in DictationPage transcription-result listener
  with try/catch

Rebrand cleanup:
- Renamed all localStorage keys from ramble_* to kon_* across
  7 files (stores, viewer, float, history)

12 tests passing, clippy clean.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/stores/page.svelte.js

@@ -12,7 +12,7 @@ export const page = $state({
 
 // ---- Settings (persisted to localStorage) ----
 
-const SETTINGS_KEY = "ramble_settings";
+const SETTINGS_KEY = "kon_settings";
 
 const defaults = {
   engine: "whisper",
@@ -53,7 +53,7 @@ export function saveSettings() {
 
 // ---- Profiles (persisted to localStorage) ----
 
-const PROFILES_KEY = "ramble_profiles";
+const PROFILES_KEY = "kon_profiles";
 
 function loadProfiles() {
   try {
@@ -73,7 +73,7 @@ export function saveProfiles() {
 
 // ---- History (persisted to localStorage) ----
 
-const HISTORY_KEY = "ramble_history";
+const HISTORY_KEY = "kon_history";
 
 function loadHistory() {
   try {
@@ -104,7 +104,7 @@ export function deleteFromHistory(index) {
 
 // ---- Tasks (persisted to localStorage) ----
 
-const TASKS_KEY = "ramble_tasks";
+const TASKS_KEY = "kon_tasks";
 
 function loadTasks() {
   try {
@@ -169,7 +169,7 @@ export function uncompleteTask(id) {
 // ---- BroadcastChannel for multi-window task sync ----
 
 const taskChannel = typeof BroadcastChannel !== "undefined"
-  ? new BroadcastChannel("ramble_tasks")
+  ? new BroadcastChannel("kon_tasks")
   : null;
 
 if (taskChannel) {
@@ -189,7 +189,7 @@ function broadcastTasks() {
 
 // ---- Task Lists (persisted to localStorage) ----
 
-const TASK_LISTS_KEY = "ramble_task_lists";
+const TASK_LISTS_KEY = "kon_task_lists";
 
 function loadTaskLists() {
   try {
@@ -309,7 +309,7 @@ export function sortTaskLists(mode) {
 
 // BroadcastChannel for task lists
 const taskListChannel = typeof BroadcastChannel !== "undefined"
-  ? new BroadcastChannel("ramble_task_lists")
+  ? new BroadcastChannel("kon_task_lists")
   : null;
 
 if (taskListChannel) {
@@ -329,7 +329,7 @@ function broadcastTaskLists() {
 
 // ---- Templates (persisted to localStorage) ----
 
-const TEMPLATES_KEY = "ramble_templates";
+const TEMPLATES_KEY = "kon_templates";
 
 function loadTemplates() {
   try {