chore: migrate routing from chi to weby

[jrozner]

Replace github.com/go-chi/chi/v5 with github.com/jrozner/weby throughout the backend. Weby wraps Go 1.22+ stdlib routing (http.ServeMux) and provides a global middleware stack.

Key changes:

• Entry points (bin/web, bin/api, bin/dev) and integration helpers now use weby.NewServeMux() with RequestID/WrapResponse/Logger middleware
• server.Web() and server.API() signatures changed from chi.Router to *http.ServeMux; inner authenticated routes wrapped with per-group middleware using handler chaining
• Route patterns updated to stdlib "METHOD /path" format; {type:regex} patterns simplified to {type} (handler already validates values)
• authschemes.AuthScheme.BindRoutes() changed from chi.Router to *http.ServeMux; all four auth scheme implementations updated
• dissectors.DissectedRequest.FromURL() now uses r.PathValue() instead of a chi url-param map; constructor signatures simplified accordingly
• Added middleware.InjectLogger() thin wrapper to inject request-scoped logger into context (used by logging.ReqLogger throughout services)
• Updated dissected_request_test.go to use r.SetPathValue() for URL param tests

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[jkennedyvz]

@jrozner can you rebase?

[jrozner]

I'm going to drop this PR and rewrite it. Would like to leave it up currently for reference.