release infra: build scripts, Firefox signing, plugin fixes

- .gitignore: release/, .env, *.xpi, node_modules/
- .env.example: template for AMO credentials
- extension-firefox/package.json: web-ext scripts (lint, sign)
- extension-firefox/manifest.json: gecko.id + update_url + data_collection_permissions
- scripts/build.sh: renamed binaries (verstak, verstak-server), release target
- scripts/sign-firefox-xpi.sh: AMO signing with --self-hosted
- scripts/release-firefox-xpi.sh: signed XPI + updates.json generation
- scripts/release.sh: full release pipeline (DEB/RPM/checksums/git tag)
- VERSION: 0.1.0
- README.md: Firefox extension & release sections

Plugin fixes:
- internal/core/plugins/manager.go: auto-create .verstak/plugins/ dir
- frontend/src/lib/SettingsSidebar.svelte: remove 'plugins' from disabled + active left border
- frontend/src/lib/SettingsPlugins.svelte: force ListPlugins refresh on toggle
- frontend/src/lib/SettingsWindow.svelte: onPluginToggle callback
- frontend/src/App.svelte: refreshSystemViews on plugin toggle
- frontend/src/lib/CalendarPluginPage.svelte: visible error icon

extension-firefox/manifest.json

@@ -9,7 +9,11 @@
   "browser_specific_settings": {
     "gecko": {
       "id": "verstak-bridge@verstak.app",
-      "strict_min_version": "109.0"
+      "strict_min_version": "115.0",
+      "update_url": "https://mirv.top/verstak/firefox/updates.json",
+      "data_collection_permissions": {
+        "required": ["none"]
+      }
     }
   },
 

extension-firefox/package.json

@@ -0,0 +1,15 @@
+{
+  "name": "verstak-bridge-firefox",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Verstak Bridge Firefox extension",
+  "scripts": {
+    "lint:firefox": "web-ext lint --source-dir .",
+    "build:firefox": "web-ext build --source-dir . --artifacts-dir ../web-ext-artifacts --overwrite-dest",
+    "sign:firefox": "../scripts/sign-firefox-xpi.sh",
+    "release:firefox": "../scripts/release-firefox-xpi.sh"
+  },
+  "devDependencies": {
+    "web-ext": "^8.0.0"
+  }
+}