Accept an iHateMoney project name where the id is expected

[Pascal-SAPUI5]

Fixes #53.

Adding an iHateMoney project by hand asks for something its web UI never shows.
iHateMoney addresses projects by an id derived from the name, so a project
called "Spongebob house" lives at spongebob-house — but the name is the only
string a user ever sees. Entering it produced a project that was added, stayed
blank, and gave no hint why. Four people reported this on #53 between 2022 and
2023.

This picks up the offer made there:

I'm happy to accept a pull request which automatically converts spaces to
dashes and lowercases the words.

What it does

The add-project form now converts what was typed the same way the server does,
mirroring slugify() in ihatemoney/utils.py:

1. NFKD-normalise, so accents can be separated from their letters
2. drop everything that is not a word character, whitespace or a hyphen —
   this is what removes the accents, and any punctuation
3. trim, lowercase
4. collapse runs of hyphens and whitespace into a single hyphen

That also explains the second half of the thread: something + somethingelse
becomes something-somethingelse, not something-+-somethingelse, because the
+ is dropped in step 2 before the gap collapses in step 4.

The conversion is idempotent, so anyone who does enter the real id is
unaffected.

Cospend is addressed by a case-sensitive share token and is deliberately left
untouched — normalising that would break every Cospend project. The choice sits
in ProjectBackend.projectIdentifier(fromUserInput:) so it is explicit and
testable rather than buried in the Combine chain.

Changes

• PayForMe/Util/Util.swift — String.iHateMoneyProjectId
• PayForMe/Model/Project.swift — ProjectBackend.projectIdentifier(fromUserInput:)
• PayForMe/Views/Projects/Manual/AddProjectManualViewModel.swift — use it when
  building the project from the form
• PayForMeTests/ProjectIdentifierTests.swift — new

Verifying

Ten tests, including both cases named in the issue:

• testASpaceBecomesAHyphen — "Spongebob house" → spongebob-house
• testPunctuationIsDroppedAndTheGapCollapses — "something + somethingelse" →
  something-somethingelse
• testAnIdThatIsAlreadyCorrectIsUnchanged — idempotence
• testCospendInputIsUntouched — a mixed-case Cospend token survives verbatim
• plus accents, repeated separators, surrounding whitespace, underscores, and
  a string with nothing usable in it

By hand: add an iHateMoney project by typing the project's name rather than its
id. It now loads.

Not covered

The thread also mentions "Could not find server" being shown when the project,
not the server, is what could not be found. That is a separate problem in how
the error is reported and is not touched here.