Add Done button, tablet controls, super admin management, midnight strike reset, and activity log improvements

- Done button snaps block to full duration, marks complete, logs "Marked Done by User"; Reset after Done fully un-completes the block
- Session action buttons stretch full-width and double height for tablet tapping
- Super admin: reset password, disable/enable accounts, delete user (with cascade), last active date per user's timezone
- Disabled account login returns specific error message instead of generic invalid credentials
- Users can change own password from Admin → Settings
- Strikes reset automatically at midnight in user's configured timezone (lazy reset on page load)
- Break timer state fully restored when navigating away and back to dashboard
- Timer no longer auto-starts on navigation if it wasn't running before
- Implicit pause guard: no duplicate pause events when switching already-paused blocks or starting a break
- Block selection events removed from activity log; all event types have human-readable labels
- House emoji favicon via inline SVG data URI
- README updated to reflect all changes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/session.py

@@ -46,3 +46,6 @@ class DashboardSnapshot(BaseModel):
     is_paused: bool = False          # whether the current block's timer is paused
     morning_routine: list[str] = []  # text items shown on TV during greeting state
     break_activities: list[str] = []  # text items shown on TV during break time
+    is_break_active: bool = False    # whether break mode is currently active
+    break_elapsed_seconds: int = 0   # seconds already elapsed in the break timer
+    is_break_paused: bool = False    # whether the break timer is paused