Add multi-user server sync (PHP server + client)

Phase 2 implementation: Multiple streamers can now merge their captions
into a single stream using a PHP server.

PHP Server (server/php/):
- server.php: API endpoint for sending/streaming transcriptions
- display.php: Web page for viewing merged captions in OBS
- config.php: Server configuration
- .htaccess: Security settings
- README.md: Comprehensive deployment guide

Features:
- Room-based isolation (multiple groups on same server)
- Passphrase authentication per room
- Real-time streaming via Server-Sent Events (SSE)
- Different colors for each user
- File-based storage (no database required)
- Auto-cleanup of old rooms
- Works on standard PHP hosting

Client-Side:
- client/server_sync.py: HTTP client for sending to PHP server
- Settings dialog updated with server sync options
- Config updated with server_sync section

Server Configuration:
- URL: Server endpoint (e.g., http://example.com/transcription/server.php)
- Room: Unique room name for your group
- Passphrase: Shared secret for authentication

OBS Integration:
Display URL format:
http://example.com/transcription/display.php?room=ROOM&passphrase=PASS&fade=10&timestamps=true

NOTE: Main window integration pending (client sends transcriptions)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

gui/settings_dialog_qt.py

@@ -147,6 +147,29 @@ class SettingsDialog(QDialog):
         display_group.setLayout(display_layout)
         main_layout.addWidget(display_group)
 
+        # Server Sync Group
+        server_group = QGroupBox("Multi-User Server Sync (Optional)")
+        server_layout = QFormLayout()
+
+        self.server_enabled_check = QCheckBox()
+        server_layout.addRow("Enable Server Sync:", self.server_enabled_check)
+
+        self.server_url_input = QLineEdit()
+        self.server_url_input.setPlaceholderText("http://example.com/transcription/server.php")
+        server_layout.addRow("Server URL:", self.server_url_input)
+
+        self.server_room_input = QLineEdit()
+        self.server_room_input.setPlaceholderText("my-room-name")
+        server_layout.addRow("Room Name:", self.server_room_input)
+
+        self.server_passphrase_input = QLineEdit()
+        self.server_passphrase_input.setEchoMode(QLineEdit.Password)
+        self.server_passphrase_input.setPlaceholderText("shared-secret")
+        server_layout.addRow("Passphrase:", self.server_passphrase_input)
+
+        server_group.setLayout(server_layout)
+        main_layout.addWidget(server_group)
+
         # Buttons
         button_layout = QHBoxLayout()
         button_layout.addStretch()
@@ -210,6 +233,12 @@ class SettingsDialog(QDialog):
         self.font_size_input.setText(str(self.config.get('display.font_size', 12)))
         self.fade_seconds_input.setText(str(self.config.get('display.fade_after_seconds', 10)))
 
+        # Server sync settings
+        self.server_enabled_check.setChecked(self.config.get('server_sync.enabled', False))
+        self.server_url_input.setText(self.config.get('server_sync.url', ''))
+        self.server_room_input.setText(self.config.get('server_sync.room', 'default'))
+        self.server_passphrase_input.setText(self.config.get('server_sync.passphrase', ''))
+
     def _save_settings(self):
         """Save settings to config."""
         try:
@@ -248,6 +277,12 @@ class SettingsDialog(QDialog):
             fade_seconds = int(self.fade_seconds_input.text())
             self.config.set('display.fade_after_seconds', fade_seconds)
 
+            # Server sync settings
+            self.config.set('server_sync.enabled', self.server_enabled_check.isChecked())
+            self.config.set('server_sync.url', self.server_url_input.text())
+            self.config.set('server_sync.room', self.server_room_input.text())
+            self.config.set('server_sync.passphrase', self.server_passphrase_input.text())
+
             # Call save callback
             if self.on_save:
                 self.on_save()