Add a daily weather system that modifies fishing yield

[dmccoystephenson]

Summary

• Adds a weather field to TimeService, rolled once per increaseDay() call from ["clear", "rainy", "stormy"] — the deferred stretch half of Make time-of-day (and optionally weather) affect fishing #72, alongside the already-shipped time-of-day modifier.
• Adds Docks.getWeatherModifier(weather) (same (factor, label) shape as getTimeOfDayModifier) and combines it into the fishToAdd calculation in Docks.fish(): rain gives a catch bonus, storms a penalty, clear is neutral.
• Surfaces the current weather in the docks descriptor text (Docks._weatherDescriptor) and in the catch report label after a fishing trip.
• Persists weather via TimeServiceJsonReaderWriter and extends schemas/timeService.json with an enum so save validation stays in sync.

Test plan

• python3 -m compileall -q src tests
• python3 -m pytest --cov=src --cov-report=term-missing --cov-report=xml:cov.xml — 351 passed
• New/updated tests cover: default weather, the daily roll (random.choice patched for determinism), schema validation (valid + out-of-enum-value rejection), reader/writer round-trip, getWeatherModifier's three branches, the fishing-yield effect, the catch-report label, and the docks descriptor text
• Front-end parity: this only adds text through the existing showOptions/prompt-text primitives already shared by all three front-ends (console/pygame/web) — no new UI primitive was needed, so no front-end-specific change was required

Closes #110

[dmccoystephenson]

Self-review: implementation matches the issue's suggested design closely. Verified all three front-ends (console/pygame/web) treat the docks descriptor and currentPrompt.text as opaque strings passed through showOptions/prompt rendering, so no front-end-specific code was needed for this change - it only adds text through existing shared primitives. Schema and reader-writer stay in sync (weather round-trips and is validated against the new enum, with a test for an out-of-enum value raising ValidationError). No logic errors or missed edge cases found. (Posted as a plain PR comment rather than a formal GitHub review since gh pr review / the pulls reviews API were blocked as requiring interactive approval in this headless session.)