Add active/inactive/game-time timers to fleet + server pages

Fleet cards and the per-server detail hero now show three live-ticking
timers: Active (since players > 0), Inactive (since server emptied), and
Game (since InitGame in games_sp.log, back-computed from the log's own
MM:SS prefix so it stays accurate across restarts). Anchors are
persisted on `servers` and fanned out via the SSE bus; a single 1s
ticker feeds every card. Idle map cycles are filtered out so the game
timer doesn't flicker.

src/lib/server/db/schema.sql

@@ -32,6 +32,14 @@ CREATE TABLE IF NOT EXISTS servers (
     image            TEXT,                                -- e.g. 'ghcr.io/ayymoss/plutainer:latest'
     created_by       TEXT,                                -- 'ui' | operator identifier
     destroyed_at     TEXT,                                -- ISO ts when tombstoned (row usually deleted; kept as safety net)
+    -- Occupancy + match timers. active_since / inactive_since are mutually
+    -- exclusive: exactly one is non-null while a server is reachable. RCON
+    -- outages do NOT clear either — timers survive transient unreachability
+    -- and resume from the same anchor when the server comes back.
+    active_since     TEXT,                                -- ISO ts of last 0 -> >0 player transition
+    inactive_since   TEXT,                                -- ISO ts of last >0 -> 0 player transition
+    game_started_at  TEXT,                                -- ISO ts we first observed InitGame: for the current match
+    game_ended_at    TEXT,                                -- ISO ts we observed ExitLevel/ShutdownGame ending it
     created_at       TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
 );