feat: poll voting, location sharing, image captions, message forwarding

- Poll voting: PollContent sends m.poll.response on answer click
- Location: MLocation shows OSM map embed + share-location button in toolbar
- Image captions: caption field on media uploads sets message body
- Message forwarding: ForwardMessageDialog with searchable room picker
- Also includes ring timeout fix and earlier session patches

src/app/components/upload-card/UploadCardRenderer.tsx

@@ -182,6 +182,27 @@ export function UploadCardRenderer({
               <PreviewVideo fileItem={fileItem} />
             </MediaPreview>
           )}
+          {(fileItem.originalFile.type.startsWith('image') ||
+            fileItem.originalFile.type.startsWith('video')) && (
+            <input
+              type="text"
+              placeholder="Add a caption… (optional)"
+              value={metadata.caption ?? ''}
+              onChange={(e) => setMetadata(fileItem, { ...metadata, caption: e.target.value })}
+              style={{
+                marginTop: '6px',
+                width: '100%',
+                background: 'var(--bg-surface-low)',
+                border: '1px solid var(--bg-surface-border)',
+                borderRadius: '6px',
+                padding: '5px 8px',
+                fontSize: '0.85rem',
+                color: 'var(--text-primary)',
+                outline: 'none',
+                boxSizing: 'border-box',
+              }}
+            />
+          )}
           {upload.status === UploadStatus.Idle && !fileSizeExceeded && (
             <UploadCardProgress sentBytes={0} totalBytes={file.size} />
           )}