feat(module): UUID-based Config.ID + table prefix

[I-am-nothing]

Summary

• `Config.ID` and the SQL table prefix now substitute from the platform-assigned UUID (`m` + 32 hex chars) instead of the URL slug
• Sanitization: strip hyphens, prepend `m` (UUIDs may begin with a digit), normalize lowercase
• Threads `module_id` through three branches in the init flow (pre-check + --used, create POST success, race re-fetch on slug_taken-after-POST)
• Pin SDK `v0.1.1` in `go.mod.tmpl`

Why

Renaming a URL slug today would orphan every Postgres schema and table prefixed from it. UUID-derived IDs are immutable, so slug rename becomes a metadata-only change.

Blocked on

• feat: allow UUID-derived module IDs (v0.1.1) app-module-sdk#94 — bumps `moduleIDPattern` to admit UUID-shape IDs. Merge that first; this PR's `go.mod.tmpl` requires the resulting `v0.1.1` tag.
• feat(module): scaffold local source tree on init #17 — base branch. Will rebase onto `main` after feat(module): scaffold local source tree on init #17 merges.

Test plan

• `cargo test` clean (42 tests, 5 new for UUID sanitization)
• `cargo clippy --all-targets -- -D warnings` clean
• `cargo fmt --all -- --check` clean
• After SDK v0.1.1 ships: scaffold to /tmp, run `go mod tidy && go build ./...`, confirm `Config.ID = "m<32 hex>"` and table is `m<32 hex>_items`

What stays slug-based

• The scaffold target dir name (`.//`) — easy to rename
• `go.mod` module path (`module `) — easy to find/replace
• `routes.go` response body (`hello from `) — user-facing, slug is the right identifier

What's UUID-derived

• `Config.ID` in main.go
• Table prefix in sql/app/0001_init.up.sql

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