burger sea sub-btn: wire .active = show_picker and not hand_complete (phase 1/3) — TDD

First slice of the "Sea sub-btn opens the spread modal" feature push.

## Server (apps/gameboard/views.py)

`my_sea` view now passes `sea_btn_active = show_picker and not hand_complete` in context. Picker phase w. cards still to draw → True; landing / sign-gate / hand-complete states → False. The condition mirrors the AUTO-DRAW-vs-GATE-VIEW state machine — sea_btn lights up exactly when AUTO DRAW is the live action btn, returns to inactive at the same moment AUTO DRAW becomes GATE VIEW + the deck FLIP gains .btn-disabled.

## Template (_partials/_burger.html)

`#id_sea_btn` conditionally renders the `.active` class:
```
<button id="id_sea_btn" type="button" class="burger-fan-btn{% if sea_btn_active %} active{% endif %}" ...>
```

Per the burger sub-btn CSS that landed in 894d65f, .active means opacity 1 + skip the --priRd inactive-click flash. The other 4 sub-btns (sky/earth/voice/text/...) remain inactive scaffolding for later sprints to wire one-by-one.

## Tests (apps/gameboard/tests/integrated/test_views.py)

3 new ITs on MySeaViewTest:
- `test_sea_btn_is_inactive_on_landing_phase` — fresh user / landing → no .active class.
- `test_sea_btn_is_active_on_picker_phase_with_partial_hand` — sig + 1-card MySeaDraw → .active class present.
- `test_sea_btn_returns_to_inactive_when_hand_complete` — 3-card spread w. all 3 positions drawn → hand_complete True → sea_btn back to inactive (regression guard for the GATE VIEW transition).

## Verification

All 12 MySeaViewTest green (+3 new). No JS / CSS touches — pure server + template change. Phase 2 (modal extraction + .sea-stacks relocate) + Phase 3 (--priYl glow handoff) land in follow-up commits.

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Sonnet 4.6 <noreply@anthropic.com>

src/apps/gameboard/views.py

@@ -348,6 +348,11 @@ def my_sea(request):
         "next_free_draw_at": next_free_draw_at,
         "hand_complete": hand_complete,
         "show_picker": show_picker,
+        # Sub-btn .active flag for the burger fan — Sea sub-btn lights up
+        # when the user is in the picker phase w. cards still to draw.
+        # As soon as hand_complete flips True (AUTO DRAW → GATE VIEW + the
+        # deck FLIP gets .btn-disabled) the Sea sub-btn returns to inactive.
+        "sea_btn_active": show_picker and not hand_complete,
         "show_paid_draw": show_paid_draw,
         "show_gate_view": show_gate_view,
         "deposit_reserved": deposit_reserved,