ADFA-5035: Fix WebServer occasionally failing to start with EADDRINUSE (#1634)

* ADFA-5035: Fix WebServer occasionally failing to start with EADDRINUSE

start() binds serverSocket on a background thread (launched from
MainActivity.startWebServer()); stop() (called from onDestroy(), main
thread) only closes serverSocket if it's already initialized. If
stop() runs before start() reaches bind(), it's a silent no-op --
start() then binds anyway a moment later, orphaned, holding the port
until the process dies. The next start() attempt on that port fails
with "Address already in use."

Synchronize start()'s bind and stop()'s close on a shared lock, and
have stop() record that a stop was requested so start() can abort
before binding if one arrived first. Closes the race window instead of
relying on timing.

Also renamed HTTP_INTERNAL_SERVER_ERROR/HTTP_NOT_FOUND to camelCase
(pre-existing ktlint property-naming violations, unrelated to this fix
but required once this file falls under the Spotless ratchet).

* ADFA-5035: Apply Spotless ratchet reformat to WebServer.kt

WebServer.kt was space-indented and had several pre-existing
ktlint violations (max-line-length, snake_case sql_query). Touching
the file in the previous commit pulled it under the Spotless ratchet,
so bring it into compliance: tabs, wrapped long lines/comments, and
sql_query -> sqlQuery. No behavioral change.

* ADFA-5035: Address code review findings

- Close database in start()'s finally alongside serverSocket. It was
  opened before the stopRequested check that can now abort start()
  early, and was never closed on any other shutdown path either
  (normal accept-loop exit, exception) -- isInitialized guards the
  case where opening it failed and this finally still runs.
- Correct stop()'s doc comment: it's no longer a full no-op before
  start() binds -- it still records the stop request so start() can
  abort before binding, which is the fix itself. Only the socket-close
  side stays a no-op in that case. (Reverting the behavior back to a
  literal no-op, as literally suggested, would reopen the exact
  EADDRINUSE race this ticket fixes.)
- Add WebServerTest: deterministic coverage for both lifecycle
  orderings (stop-before-start aborts the bind; start-then-stop frees
  the port for reuse), synchronized via the port's own bind/connect
  behavior rather than fixed sleeps.

Skipped: the outputStarted-timing suggestion for realHandleBsEndpoint/
realHandlePrEndpoint is the same CodeRabbit finding already considered
and explicitly rejected in an existing code comment ("I disagree...
--DS, 23-Feb-2026"); out of scope to unilaterally revisit here.

* ADFA-5035: Fix outputStarted timing in handleBsEndpoint/handlePrEndpoint

outputStarted was only set after realHandleBsEndpoint/realHandlePrEndpoint
returned, so if writeNormalToClient threw partway through (e.g. after
the status line but mid-body), the catch block still saw
outputStarted=false and sent a second, well-formed response on top of
the already-partially-written one.

Pass a markOutputStarted callback into both functions and invoke it
right before the first write, so the caller's flag reflects reality
even when the write itself then fails.

Removes the "I disagree with CodeRabbit's message" comment that had
left this finding unaddressed.

Author: davidschachterADFA