- Document new data directory path for profiles
- Add duplicate prevention and refresh workflow
- Document deleted profile behavior in dashboard and settings
- Document Docker volume mount, legacy path auto-migration
- Document account-level dedup by external_id

…y, SMTP/push diagnostics (#37)

**Navbar simplification:**
- Replace horizontal Codex profile buttons with compact dropdown
- Remove timezone badge, password button, and layout toggle from navbar
- Move layout density control to Settings > General tab
- Remove welcome subtitle ("Track your ... API quota usage")

**Notification granularity:**
- Add per-quota notification type toggles (Warn/Crit/Reset checkboxes) on override rows
- Backend persists disable_reset, disable_warning, disable_critical per override
- All 8 providers available in override dropdown (was 4)
- Fix Antigravity to send notifications per quota group instead of per model
- Fix MiniMax to send single notification for shared pool instead of 24+ duplicates

**SMTP & Push diagnostics:**
- SMTP test now performs full handshake (MAIL FROM, RCPT TO) with diagnostic output
- Single connection for diagnostics + send (no double-connect)
- Push diagnostics panel shows protocol, SW status, VAPID key, subscription state
- Diagnostics collect even on non-HTTPS (most useful when push is broken)

**MiniMax improvements:**
- Consolidate chart to single "MiniMax Coding Plan" line (was 24+ model lines)
- Remove "Shared: ..." model list from quota card and insight stats
- Clean session history: remove redundant Session column, rename headers,
  add percentage to Peak Requests, Active badge in Ended column
- Single notification override entry for shared pool

**Other fixes:**
- Change pace wording from "in deficit" to "over pace"
- Remove ~95 lines of orphaned CSS (old modal, layout toggle, timezone badge)
- Fix mobile dropdown positioning, override row wrapping
- Update E2E tests for settings-based password management
- Clean up dead password modal JS code

GitHub updated the macos-14 runner image (20260317.0174) which broke
the systray CGo build due to SDK type mismatches in CoreText/AppKit.
Pin Xcode 16.2 to ensure consistent SDK behavior.

xcode-select alone isn't enough - CGo still uses CommandLineTools SDK.
Explicitly set SDKROOT to the Xcode SDK path via xcrun.

macos-14 runner image update (20260317.0174) broke CGo/systray builds
due to CommandLineTools SDK incompatibility. Switch to macos-15 which
has a working default Xcode/SDK configuration.