Move remaining inline icon SVGs into the shared icon module #314

Follow-up to #208. The icon-module stack (#276 → #305 → #306 → #307) covers most call sites. These inline icons are left; some were added to main while the stack was in review:

• src/components/TaskProjectFilter.tsx
• src/graph/GraphCanvas.tsx (lock glyph only, not the canvas surface)
• src/graph/KindMark.tsx
• src/components/understanding/TourOutline.tsx
• src/documents/FilesPopover.tsx

Each should use (or add) a component in src/components/icons.tsx, with the glyph unchanged.

Out of scope: these are not icons, so they stay inline:

• src/components/chat/ContextMeter.tsx: data ring
• src/components/MergeCommitList.tsx: accent-coloured dot
• src/lib/mermaid-lightbox.ts: HTML built as strings

Please wait for the #208 stack to land before starting, to avoid conflicts.