refactor(commands): replace hand-rolled fetch-with-timeout blocks with helpers

[Rushaway]

Summary

• Five near-identical blocks in Commands.py (WolframAlpha, UrbanDictionary, OpenWeather, WUnderground ×2) each opened their own ClientSession and wrapped both the request and the body read in asyncio.wait_for. aiohttp provides that natively via ClientTimeout, so the wait_for wrappers were redundant scaffolding repeated five times.
• Added Utils.FetchJson / Utils.FetchText, which own the session and the timeout budget, and switched all five sites over.

Notes on scope and behavior

• URLInfo.get_url_data deliberately keeps its own session. It needs response headers plus a bounded 64 KB read, so forcing it into the shared helper would mean a third helper shape used by exactly one caller. Its redundant wait_for pair is replaced with a ClientTimeout though, since that's the same underlying point.
• FlareSolverr is no longer part of this pattern — the issue listed it, but fix(flaresolverr): reuses a pooled session instead of opening one per call #144 already moved it to a pooled session with its own timeout. Outdated by the time I got here.
• The helpers let exceptions propagate rather than swallowing them, so the two WUnderground sites keep their existing try/except and their user-facing "Failed to retrieve data" message. Verified a timeout still surfaces as asyncio.TimeoutError — the exact type asyncio.wait_for raised — so those handlers behave identically.
• Dropped the if not resp: return N guards, which were dead code: aiohttp.ClientResponse defines neither __bool__ nor __len__, so it's always truthy. Each site keeps its reachable if not data code.

Closes #152

Test plan

Ran the helpers against a live local aiohttp server:

• FetchJson returns parsed JSON.
• FetchJson(params=...) forwards query params correctly.
• FetchText returns the body text.
• A slow endpoint with timeout=0.5 raises asyncio.TimeoutError (same exception type as before, so existing handlers still catch it).
• Removed the now-unused aiohttp import from Commands.py and asyncio from URLInfo.py (ruff F401 would otherwise fail CI).

🤖 Generated with Claude Code

[Rushaway]

Self-review: the thing I was most careful about is that the helper does NOT swallow exceptions -- if it did, WUnderground's try/except and its user-facing error message would silently stop firing. Verified against a live server that a timeout still raises asyncio.TimeoutError, the same type wait_for raised, so those handlers are unaffected. Also note I left URLInfo out of the shared helper on purpose (it needs headers + a capped read) and that FlareSolverr had already dropped out of this pattern in #144.

[Dolly132]

Tested, works fine as intended.