feat: equalizer profiles in the web interface

Add selectable equalizer profiles on top of the existing 3-band tone
control (low/band/high pass gain). A profile dropdown in the equalizer
modal switches presets:

- Flat (neutral)
- Music (fuller bass)
- Audiobook / Speech (cuts bass, lifts mids/highs)
- Deep voices (stronger mid/high boost for low narrator voices)
- Custom (manual sliders)

The speech-oriented profiles improve intelligibility of deep narrator
voices, where the fundamental sits low but clarity lives in the
mids/highs. The active profile is persisted in NVS (eqProfile) and
restored in the UI; moving a slider switches to Custom. Gains still
drive playback via Audio.setTone() unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: fhirschmann

README.md

@@ -66,6 +66,7 @@ neon logo that doubles as the SVG favicon ([`8d9725c`](../../commit/8d9725c)):
 | --- | --- |
 | PWA support: web app manifest + app icon, "add to home screen" with proper icon and name | [`a59fe0b`](../../commit/a59fe0b) |
 | Full backup: export/import of all settings + RFID assignments as JSON, WiFi credentials optional | [`7f2e4ae`](../../commit/7f2e4ae) |
+| Equalizer profiles: dropdown presets (Flat / Music / Audiobook-Speech / Deep voices / Custom) on top of the 3-band tone control; speech presets cut bass and lift mids/highs so deep narrator voices stay intelligible, persisted in NVS. Profiles can also be assigned per file or directory (right-click in the file browser) — e.g. set the speech profile for all Bibi Blocksberg episodes at once. The active profile can be cycled with the bindable command **154** (button/RFID modifier) and set/reported via the MQTT topic `equalizer` (`flat`/`music`/`speech`/`voiceBoost`) | [`300b9dd`](../../commit/300b9dd) |
 | SD card cleanup: removes macOS metadata (`.DS_Store`, `._*`, Spotlight/Trashes) with one click | [`5f38a51`](../../commit/5f38a51) |
 | Live log: the log dialog refreshes every 2 s and follows the end of the log | [`d326faa`](../../commit/d326faa) |
 | Drag & drop: upload files by dropping them from the file manager onto the file tree | [`e4972fe`](../../commit/e4972fe) |

html/locales/de.json

@@ -175,7 +175,9 @@
 			"refresh": "Aktualisieren",
 			"delete": "Löschen",
 			"rename": "Umbenennen",
-			"download": "Herunterladen"
+			"download": "Herunterladen",
+			"eq": "EQ-Profil",
+			"eqRemove": "Kein EQ (entfernen)"
 		},
 		"files": {
 			"title": "Dateien",
@@ -259,6 +261,7 @@
 					"151": "IP-Adresse ansagen",
 					"152": "Uhrzeit ansagen",
 					"153": "Ambient Light umschalten",
+					"154": "Equalizer-Profil durchschalten",
 					"0": "Lösche Zuordnung",
 					"170": "Play/Pause",
 					"171": "Vorheriger Titel",
@@ -402,10 +405,18 @@
 		},
 		"equalizer": {
 			"title": "Equalizer",
+			"profile": {
+				"title": "Profil",
+				"flat": "Neutral (linear)",
+				"music": "Musik (kräftiger Bass)",
+				"speech": "Hörbuch / Sprache",
+				"voiceBoost": "Tiefe Stimmen (max. Verständlichkeit)",
+				"custom": "Benutzerdefiniert"
+			},
 			"gainLowPass": "Tiefen (in dB)",
 			"gainBandPass": "Mitten (in dB)",
 			"gainHighPass": "Höhen (in dB)",
-			"info": "Die Frequenzen sind laut Bibliothek (ESP32-audioI2S) 500 Hz LowShelf, 3000 Hz PeakEQ und 6000 Hz HighShelf."
+			"info": "Die Frequenzen sind laut Bibliothek (ESP32-audioI2S) 500 Hz LowShelf, 3000 Hz PeakEQ und 6000 Hz HighShelf. Die Profile „Hörbuch / Sprache“ und „Tiefe Stimmen“ senken den Bass und heben Mitten/Höhen an, damit tiefe Erzählerstimmen besser verständlich sind."
 		},
 		"rfid": {
 			"title": "RFID Reader",
@@ -477,6 +488,11 @@
 		}
 	},
 	"tools": {
+		"eqrules": {
+			"title": "EQ-Regeln (pro Datei/Ordner)",
+			"desc": "Übersicht der per-Pfad zugewiesenen Equalizer-Profile. Hier kannst du sie ansehen und löschen.",
+			"empty": "Keine EQ-Regeln gesetzt."
+		},
 		"backup": {
 			"title": "Backup",
 			"desc": "Exportiert bzw. importiert alle Einstellungen und RFID-Zuweisungen als JSON-Datei.",

html/locales/en.json

@@ -176,7 +176,9 @@
 			"refresh": "Refresh",
 			"delete": "Delete",
 			"rename": "Rename",
-			"download": "Download"
+			"download": "Download",
+			"eq": "EQ profile",
+			"eqRemove": "No EQ (remove)"
 		},
 		"files": {
 			"title": "Files",
@@ -260,6 +262,7 @@
 					"151": "Announce IP-Address",
 					"152": "Announce current time",
 					"153": "Toggle Ambient Light",
+					"154": "Cycle equalizer profile",
 					"0": "Remove assignment",
 					"170": "Toggle Play/Pause",
 					"171": "Previous track",
@@ -403,10 +406,18 @@
 		},
 		"equalizer": {
 			"title": "Equalizer",
+			"profile": {
+				"title": "Profile",
+				"flat": "Flat (neutral)",
+				"music": "Music (fuller bass)",
+				"speech": "Audiobook / Speech",
+				"voiceBoost": "Deep voices (max. clarity)",
+				"custom": "Custom"
+			},
 			"gainLowPass": "Lows (in dB)",
 			"gainBandPass": "Mids (in dB)",
 			"gainHighPass": "Highs (in dB)",
-			"info": "According to the library (ESP32-audioI2S), the frequencies are 500 Hz LowShelf, 3000 Hz PeakEQ and 6000 Hz HighShelf."
+			"info": "According to the library (ESP32-audioI2S), the frequencies are 500 Hz LowShelf, 3000 Hz PeakEQ and 6000 Hz HighShelf. The \"Audiobook / Speech\" and \"Deep voices\" profiles cut the bass and lift mids/highs so deep narrator voices stay intelligible."
 		},
 		"rfid": {
 			"title": "RFID Reader",
@@ -479,6 +490,11 @@
 		}
 	},
 	"tools": {
+		"eqrules": {
+			"title": "EQ rules (per file/folder)",
+			"desc": "Overview of the per-path equalizer profiles. View and delete them here.",
+			"empty": "No EQ rules set."
+		},
 		"backup": {
 			"title": "Backup",
 			"desc": "Exports or imports all settings and RFID assignments as a JSON file.",

html/locales/fr.json

@@ -168,7 +168,9 @@
 			"refresh": "Actualiser",
 			"delete": "Supprimer",
 			"rename": "Renommer",
-			"download": "Télécharger"
+			"download": "Télécharger",
+			"eq": "Profil EQ",
+			"eqRemove": "Pas d'EQ (retirer)"
 		},
 		"files": {
 			"title": "Fichiers",
@@ -253,6 +255,7 @@
 					"152": "Annoncer l'heure actuelle",
 					"0": "Supprimer l'affectation",
 					"153": "Basculement de la lumière ambiante",
+					"154": "Changer de profil d'égaliseur",
 					"170": "Basculer Lecture/Pause",
 					"171": "Piste précédente",
 					"172": "Piste suivante",
@@ -395,10 +398,18 @@
 		},
 		"equalizer": {
 			"title": "Égaliseur",
+			"profile": {
+				"title": "Profil",
+				"flat": "Neutre (linéaire)",
+				"music": "Musique (basses renforcées)",
+				"speech": "Livre audio / Voix",
+				"voiceBoost": "Voix graves (clarté maximale)",
+				"custom": "Personnalisé"
+			},
 			"gainLowPass": "Graves (en dB)",
 			"gainBandPass": "Médiums (en dB)",
 			"gainHighPass": "Aigus (en dB)",
-			"info": "Les fréquences sont, selon la bibliothèque (ESP32-audioI2S), 500 Hz LowShelf, 3000 Hz PeakEQ et 6000 Hz HighShelf."
+			"info": "Les fréquences sont, selon la bibliothèque (ESP32-audioI2S), 500 Hz LowShelf, 3000 Hz PeakEQ et 6000 Hz HighShelf. Les profils « Livre audio / Voix » et « Voix graves » réduisent les basses et rehaussent les médiums/aigus pour que les voix de narrateurs graves restent intelligibles."
 		},
 		"rfid": {
 			"title": "RFID Reader",
@@ -466,6 +477,11 @@
 		}
 	},
 	"tools": {
+		"eqrules": {
+			"title": "Règles EQ (par fichier/dossier)",
+			"desc": "Aperçu des profils d'égaliseur attribués par chemin. Vous pouvez les consulter et les supprimer ici.",
+			"empty": "Aucune règle EQ définie."
+		},
 		"backup": {
 			"title": "Sauvegarde",
 			"desc": "Exporte ou importe tous les réglages et attributions RFID dans un fichier JSON.",