Add pronoun personalization to Recommendation Letter Generator

[Copilot]

Adds a required Pronouns field to the letter generator form and threads the selected pronouns through every generated paragraph so letters read as personally written for the specific student.

Form Changes

• New pronounSelect dropdown (required, positioned after name fields): He/Him, She/Her, They/Them, Prefer not to answer
• Pronoun selection validated before generation; clearBtn resets it

Pronoun Engine

• getPronouns(selection, firstName) → returns { subj, obj, poss, subjCap, is, has, … }. For Prefer not to answer, all pronoun slots resolve to firstName / firstName + "'s" — no pronouns ever surface in the output.
• fillTemplate(text, firstName, p) — replaces {P_SUBJ}, {P_OBJ}, {P_POSS}, {P_SUBJ_CAP}, {P_IS}, {P_HAS} tokens in any string.

// they/them example
{ subj: 'they', obj: 'them', poss: 'their', subjCap: 'They', is: 'are', has: 'have' }

// prefer not to answer — "Jordan Rivera" student
{ subj: 'Jordan', obj: 'Jordan', poss: "Jordan's", subjCap: 'Jordan', is: 'is', has: 'has' }

Template Updates

All student-referencing they/them/their replaced with {P_*} tokens across:

• TRANSITIONS, all 15 TRAIT_PHRASES entries, OPENINGS (×7), CLOSINGS (×6), PURPOSE_DATA closingStatements (all 7 purposes)
• buildTraitParagraph() now accepts and applies p
• generateLetter() reads/validates pronouns, constructs p, passes it to every template

One existing phrase — "a consistent effort to lift teammates up rather than stand apart from them" — was rewritten to remove the ambiguous them (referred to teammates, not the student) to prevent incorrect substitution.