feat: redesign authenticated UI with home overview and settings hub

- Add HomePage with open sessions grid, projects overview, and session composer
- Add SettingsPage with tabs for General, SSH Keys, Tool Types, Tool Configs
- Update navigation to Home, Projects, Settings
- Redirect legacy routes (/sessions, /ssh-keys, /tool-types, /tool-configs)
- Apply Inter font and warm editorial styling
- Update tests for new dashboard and projects pages

Quality gates: typecheck pass, lint pass, 15/15 tests pass

Refs: openspec/changes/ui-redesign-home-settings

openspec/changes/ui-redesign-home-settings/design.md

@@ -0,0 +1,106 @@
+# UI Redesign - Design
+
+## Information Architecture
+
+```
+App
+├── Home
+│   ├── Hero / status
+│   ├── Open sessions
+│   ├── Available projects
+│   └── Session creation
+├── Projects
+├── Settings
+│   ├── General
+│   ├── SSH Keys
+│   ├── Tool Types
+│   └── Tool Configs
+└── Legacy routes
+    └── Redirect to new locations
+```
+
+## Home Page
+
+### Purpose
+
+Provide a fast, glanceable overview of the user's active work.
+
+### Sections
+
+1. **Hero**
+   - Greeting
+   - Short status line
+   - Primary actions: New Project, Open Session, Settings
+
+2. **Summary strip**
+   - Small count cards for sessions, projects, and tooling state
+
+3. **Open Sessions**
+   - Primary section
+   - Session cards with project, repository, tool type, status, and actions
+
+4. **Available Projects**
+   - Secondary section
+   - Project cards with quick entry into the project workspace
+
+5. **Session composer**
+   - Optional compact create flow if it fits the page cleanly
+
+## Settings Page
+
+### Layout
+
+Tabbed shell with one content area and four tabs:
+
+- General
+- SSH Keys
+- Tool Types
+- Tool Configs
+
+### Tab Responsibilities
+
+**General**
+- Theme
+- Git identity
+- Default editor
+
+**SSH Keys**
+- List keys
+- Create key
+- Copy public key
+- Delete key
+
+**Tool Types**
+- Browse tool catalog
+- Edit custom tool types
+- Delete custom tool types
+
+**Tool Configs**
+- Browse per-tool configurations
+- Add/edit/delete configs
+- Keep the existing config model and API behavior
+
+## Visual Direction
+
+- Font: Inter for UI text
+- Code font: monospace only for technical fields
+- Palette: warm light surfaces, forest green primary, muted utility accents
+- Dark mode: charcoal surfaces with softened accents
+- Styling: editorial, structured, high-contrast hierarchy, minimal chrome
+
+## Routing
+
+- `/` -> Home
+- `/sessions` -> redirect to `/`
+- `/settings` -> General tab
+- `/settings/ssh-keys` -> SSH Keys tab
+- `/settings/tool-types` -> Tool Types tab
+- `/settings/tool-configs` -> Tool Configs tab
+- legacy `/ssh-keys`, `/tool-types`, `/tool-configs` -> redirect to settings tabs
+
+## Component Strategy
+
+- Reuse shell and existing APIs
+- Replace the dashboard page with the new home overview
+- Convert the settings layout into a shared tab shell
+- Keep changes focused to the frontend layer