refactor: restructure app components by platform and feature

[ivan-jukic]

What

Replaces frontend/app/src/{components,components_mobile,components_shared} with:

src/
  desktop/   features/ + shared/ + shell/ + ui/
  mobile/    features/ + shared/ + shell/ + ui/
  ui/        cross-platform primitives (see STRAGGLERS.md)

Features: chats/ umbrella (core = kind-agnostic message engine, thread, pinned, group, community, members), plus chatlist, bots, profile, wallet, access, proposals, onboard, landing, etc. Same taxonomy in both platform trees.

• 979 files moved, 3413 imports rewritten in 782 files
• 33 dead files deleted (zero importers; one had imports of files that don't exist)
• @shared_components alias removed (vite + tsconfig)
• new eslint rule local/structure-boundaries:
  • error: desktop/ ↛ mobile/ (either direction), src/ui ↛ platform trees
  • warn: cross-feature imports — allowed only via a feature's exports/ (e.g. bots/exports/BotBadge.svelte) or features/chats/core/**; 149 pre-existing violations are the baseline to burn down, then flip to error

How placements were decided

Computed from the import graph, not by hand: a component lives with the only feature that imports it; multi-feature consumers → platform shared/; consumers in both trees → src/ui + entry in ui/STRAGGLERS.md; no importers → deleted. Human input was a 33-entry seed map (panel roots and Home-mounted modals whose only importer is the shell) and the folder→feature mapping.

Verification

• svelte-check: 4716 files, 0 errors
• eslint: 0 errors (152 warnings: 149 boundary baseline + 3 pre-existing)
• vitest: 372/372
• rollup production build succeeds; frontend build manually tested
• git log --follow traces history through the renames

Follow-ups (not this PR)

• Review the 12 components in ui/STRAGGLERS.md — promote or fork per platform
• Burn down the 149 cross-feature warnings, then set the rule to error
• Pre-existing smells surfaced by parsing svelte in eslint (silenced per-rule here): duplicate case label desktop/shell/Home.svelte:450, case fallthrough chats/core/PreviewFooter.svelte:103, async promise executor profile/ViewUserProfileModal.svelte:69

🤖 Generated with Claude Code

https://claude.ai/code/session_01MvT4UYdWURffYxsCHowXFy

[github-actions]

canbench 🏋 (dir: .)

./canbench_results.yml is up to date ✅

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Benchmark: add_reactions
  total:
    instructions: 1.36 B (0.00%) (change within noise threshold)
    heap_increase: 5 pages (no change)
    stable_memory_increase: 0 pages (no change)

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Benchmark: push_simple_text_messages
  total:
    instructions: 207.96 M (0.03%) (change within noise threshold)
    heap_increase: 12 pages (no change)
    stable_memory_increase: 0 pages (no change)

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