feat(quick-260914-m97): Fehler-melden-Knopf in der Kopfzeile — Bildschirmfoto vor dem Dialog (html-to-image 1.11.13), Fehlerpuffer, Dialog mit Vorschau, i18n bugReport

- Knopf (Kaefer-Symbol) unmittelbar vor dem Erscheinungsbild-Schalter; captureScreenshot() laeuft VOR dem Oeffnen, Test pinnt es im toPng-Mock
- computeCaptureSize (laengste Kante 1600 px, reine Funktion, getestet), dataUrlToBlob, sendBugReport als Multipart mit credentials und ohne Content-Type-Header
- error-buffer: Ringpuffer 20, window error/unhandledrejection, console.error (Original bleibt), fetch-Wrapper nur bei !ok ohne Anfrage-Rumpf/Suchteil/Kopfzeilen (T-M97-02), idempotent, SSR-sicher; installiert in app-shell
- Dialog mit Vorschau, Haekchen, Beschreibung, Meldungen je Status 409/413/429/502/allgemein, Admin-Link auf /admin/smtp
- i18n bugReport de/en, Allowlist um "passiert"; html-to-image exakt 1.11.13, Lockfile aktualisiert

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018N9CD3ebPKm1b32bPpBknY

apps/web/src/messages/en.json

@@ -483,6 +483,28 @@
     "dark": "Dark",
     "system": "System"
   },
+  "bugReport": {
+    "button": "Report a problem",
+    "title": "Report a problem",
+    "intro": "Tessera has just taken a picture of this page – it shows exactly what you see. The picture, your description, the page, version, browser and the most recent error messages are sent by e-mail to your administrator.",
+    "screenshotAlt": "Screenshot preview",
+    "screenshotUnavailable": "No screenshot possible – the report will be sent without a picture.",
+    "attachScreenshot": "Attach screenshot",
+    "descriptionLabel": "What happened?",
+    "descriptionPlaceholder": "Optional: What did you do, what did you expect, what happened instead?",
+    "send": "Send",
+    "sending": "Sending…",
+    "cancel": "Cancel",
+    "close": "Close",
+    "sent": "Thank you, your report has been sent.",
+    "errorNotConfigured": "No mailbox has been set up for bug reports yet.",
+    "errorNotConfiguredAdminHint": "Set the address under Administrator → SMTP in the field \"Bug reports to\".",
+    "errorNotConfiguredAdminLink": "Go to the SMTP settings",
+    "errorTooMany": "Too many reports in a short time. Please try again in a few minutes.",
+    "errorTooLarge": "The picture is too large. Please send the report without the screenshot.",
+    "errorSendFailed": "The e-mail could not be sent. Please try again later or contact your administrator.",
+    "errorGeneric": "The report could not be sent."
+  },
   "locale": {
     "de": "Deutsch",
     "en": "English"