MAINT-13: a full pack that stops at 98-99 % is not a failed charge

A charge is complete at SoC >= target, or at >= target - 3 once the SoC has
made no new high for 60 min of allowed charging, or when the charging time
runs out at >= target - 3. The 36 h timeout counts only the minutes the price
gate let the pack charge (plus a 7 day wall-clock backstop). A cycle that
fails (stuck drain, charge below target - 3) backs off 7 days, tells the
operator once (EN + NL), and no cycle starts on that pack in that time unless
the operator forces one. State survives a restart; old state files load.

No option added. DECISIONS/MAINT-13-full-pack-is-complete.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/app/store.py

@@ -94,6 +94,7 @@ DEFAULTS = {
     "phase_started": None,
     "last_completed": None,
     "last_start_attempt": None,
+    "last_failed": None,
     "sign_tripped": False,
     "sign_reason": "",
     "circ_tripped": False,
@@ -171,7 +172,7 @@ MAINT_SCHEMA_KEY = "maint_schema_version"
 # silently stop being migrated - the same property `UNIT_STORE_KEYS` gives the
 # SAFETY-02 pair.
 MAINT_UNIT_KEYS = ("phase", "phase_started", "last_completed",
-                   "last_start_attempt")
+                   "last_start_attempt", "last_failed")
 
 
 def unit_key(unit: str, key: str) -> str: